Method and apparatus for forming tow-based absorbent structures with a single casing sheet

ABSTRACT

An apparatus and method for forming tow-based absorbent structures having a single casing sheet are disclosed. The apparatus has a tow supply mechanism for providing tow material, a particulate matter supply mechanism for providing particulate matter, and a casing sheet supply mechanism for providing casing sheet material. The apparatus also has a vacuum draw roll having a foraminous center surface that has a width defined by a first edge and a second edge and is rotatable about a first axis. The vacuum draw roll is positioned to receive the tow material, the particulate matter and the casing sheet material to form a open core composite supply. The apparatus also has one or more angled surfaces positioned to create one or more obtuse angles in the open core composite supply, and one or more folders to further fold the one or more obtuse angles in the open core composite supply to form a folded core composite supply.

This application is a continuation-in-part of U.S. Ser. No. 10/046,279,filed Jan. 16, 2002, now U.S. Pat. No. 6,832,905.

FIELD OF THE INVENTION

The present invention relates generally to systems and methods formanufacturing absorbent garment cores. More specifically, the presentinvention relates to a system and method for forming tow-based absorbentstructures having a single casing sheet.

BACKGROUND OF THE INVENTION

Disposable absorbent garments such as infant diapers or training pants,adult incontinence products and other such products typically wereconstructed with a moisture-impervious outer backsheet, amoisture-pervious body-contacting inner topsheet, and amoisture-absorbent core sandwiched between the liner and backsheet.

Much effort has been expended to find cost-effective materials forabsorbent cores that display good liquid absorbency and retention.Particles of superabsorbent materials (SAP) in the form of granules,beads, fibers, bits of film, globules, etc., have been favored for suchpurposes. Such SAP materials generally are polymeric gelling materialsthat are capable of absorbing and retaining even under moderate pressurelarge quantities of liquid, such as water and body wastes, relative totheir weight. The SAP particles typically have been distributed within afibrous web of fluffed pulp material, which may comprise natural orsynthetic fibers. Such absorbent structures are commonly referred to asfluff pulp/SAP cores.

Superabsorbent material generally is a water-insoluble butwater-swellable polymeric substance capable of absorbing water in anamount that is greater than the weight of the substance in its dry form.In one type of superabsorbent material, the particles may be describedchemically as having a back bone of natural or synthetic polymers withhydrophilic groups or polymers containing hydrophilic groups beingchemically bonded to the back bone or an intimate admixture therewith.Included in this class of materials are modified polymers such as sodiumneutralized cross-linked polyacrylates and polysaccharides including,for example, cellulose and starch and regenerated cellulose that aremodified to be carboxylated, phosphonoalkylated, sulphoxylated orphosphorylated, causing the SAP to be highly hydrophilic. Such modifiedpolymers also may be cross-linked to reduce their water-solubility.

The ability of a superabsorbent material to absorb liquid is dependentupon the form, position and/or manner in which particles of thesuperabsorbent material are incorporated into the fibrous web of theabsorbent core. Whenever a particle of the superabsorbent material iswetted, it swells and forms a gel. Gel formation can block liquidtransmission into the interior of the absorbent core, a phenomenoncalled “gel blocking.” Gel blocking prevents liquid from rapidlydiffusing or wicking past the “blocking” particles of superabsorbent,causing portions of a partially hydrated core to become inaccessible tomultiple doses of urine. Further absorption of liquid by the absorbentcore must then take place via a diffusion process. This is typicallymuch slower than the rate at which liquid is applied to the core. Gelblocking often leads to leakage from the absorbent article well beforeall of the absorbent material in the core is fully saturated.

Despite the incidence of gel blocking, superabsorbent materials arecommonly incorporated into absorbent cores because they absorb andretain large quantities of liquid, even under load. However, in orderfor superabsorbent materials to function, the liquid being absorbed inthe absorbent structure must be transported to unsaturatedsuperabsorbent material. In other words, the superabsorbent materialmust be placed in a position to be contacted by liquid. Furthermore, asthe superabsorbent material absorbs the liquid it must be allowed toswell. If the superabsorbent material is prevented from swelling, suchas by being tightly constrained within the fibrous web or by pressureexerted by the swelling of adjacent superabsorbent particles, it willcease absorbing liquids.

Adequate absorbency of liquid by the absorbent core at the point ofinitial liquid contact and rapid distribution of liquid away from thispoint are necessary to ensure that the absorbent core has sufficientcapacity to absorb subsequently deposited liquids. Previous absorbentcores have thus attempted to absorb quickly and distribute largequantities of liquids throughout the absorbent core while minimizing gelblocking during absorption of multiple doses of liquid.

Some of the more important performance attributes of an absorbent coreof a diaper (or any other absorbent garment) are functional capacity,rate of absorption, and core stability in use. Absorption under load orAUL is a good measure of functional capacity and the rate at which thatabsorption occurs. AUL is a function of both SAP basis weight (mass perunit area) and the composition of SAP used in the composite.Conventional baby diaper cores that contain only a fibrous web of fluffpulp and a high gel strength SAP typically maintain adequate SAPefficiency if the core contains less than about 50% SAP. Fluff/SAPdiaper cores containing more than 50% SAP generally result in lower SAPefficiency because of gel blocking. Although fluff/SAP cores at greaterthan 50% SAP can provide adequate absorbency, the overall basis weightof the core typically must be increased to compensate for the lowerefficiency of the SAP. Increasing the basis weight decreases theperformance/cost ratio of the absorbent core, making them uneconomical.Also, increased basis weights tend to affect the fit and comfort of thegarment, as well as impacting the packaging and shipping costs.

Attempts to increase the relative weight of SAP by reducing the basisweight of the conventional fluff pulp have resulted in failure becauselow density fluff pulp mats have been unable to withstand the tensileloads placed on them during the manufacturing process. Such cores alsoexhibit poor wet strength, making them unstable during use, and fail toadequately secure the SAP in place. The introduction of relatively highintegrity fibrous structure cores, however, has allowed the basis weightof the fibrous web to be decreased without compromising themanufacturability and wet strength of the absorbent core. Theseabsorbent core structures have improved SAP efficiency and a loweroverall basis weight. Such absorbent cores are disclosed, for example,in U.S. Statutory Invention Registration No. H1,565 to Brodof et al.,which is incorporated by reference herein in its entirety and in amanner consistent with the present invention. These high integrityfibrous structure cores, referred to herein as “tow/SAP” cores or“tow-based” cores, typically use a continuous tow of crimped filaments.The tow may be provided to the absorbent core manufacturer in a compactform and “opened” (i.e., “bloomed” or fluffed up) prior to beingassembled into an absorbent core.

In some cases, the fibrous web of the tow/SAP core may be treated with atackifying agent to adhere the SAP particles to the fibrous web. Inother cases, the SAP particles may be introduced into the fibrous webwithout any adhesive, binder or tackifying agent, such as is disclosedin U.S. Pat. No. 6,068,620 issued to Chmielewski et al., which isincorporated by reference herein in its entirety and in a mannerconsistent with the present invention. Such a construction has beenreferred to as a dry-formed composite (DFC) core. A DFC core may besurrounded by a tissue layer or multiple tissue layers to form a DFClaminate structure that contains the fibrous web and SAP. One potentialdrawback with DFC cores, however, is that known methods and apparatusfor producing such cores typically require two separate tissue sheets tobe used during manufacturing to encase the tow and SAP. The use of twotissue sheets may, for example, increase the cost or complexity of themanufacturing operation.

A problem with SAP-containing fibrous cores has been to provide the SAPinto the fibrous web in a controlled manner. Typical known processes forcreating a conventional fluff pulp/SAP core use a large forming chamberto blend the SAP with the fluffed pulp, then convey this blend onto adrum or screen by using a vacuum. The drum or screen has forming pocketsthat form the fluff pulp/SAP material into the desired shape and theformed cores then are deposited for integration into absorbent products.Such methods have been found to be inefficient during startup andtransitions in the manufacturing line speed because they require arelatively large amount of time to provide a stabilized mixture of SAPand fluff pulp, leading to the creation of a large number of scrapproducts until stabilization.

Other conventional processes for forming fluff pulp/SAP cores immersethe fluffed pulp in a fluid mixture containing SAP particles, then drythe fluff pulp/SAP mixture before integration into the absorbentarticle. Such wet forming processes typically require more manufacturingsteps and are more expensive than dry forming methods.

Other feeding systems use fixed-size moving mechanical gates thatprovide a uniform amount of SAP to the absorbent core, such as isdisclosed in U.S. Pat. No. 6,139,912 to Onuschak et al., which isincorporated herein by reference in its entirety and in a mannerconsistent with the present invention. Although such devices may besuitable for providing an even flow of SAP or other powdered andparticulate additives to absorbent cores, they rely on relativelycomplex feeding machinery, including a rotary valve that uses apneumatic SAP conveyor to return undistributed SAP back to a supplycontainer. Pneumatic conveyors typically require a relatively long timeto become pressurized and to convey the SAP, causing inefficienciesduring transitional phases, such as when the machine operating speedvaries, such as during start-up and shut-down, or when it is desired tochange the amount of SAP being fed to the core. The additional parts ofsuch feeders may also be expensive and subject to wear and other serviceproblems. Similar devices, having similar deficiencies, are disclosed inU.S. Pat. No. 4,800,102 to Takada, which is incorporated herein byreference in its entirety and in a manner consistent with the presentinvention.

Still other feeding systems use pneumatic particle projectors that usepressurized gas to convey the SAP to the surface of the absorbent core.Such devices are disclosed, for example, in U.S. Pat. Nos. 5,614,147 toPelley and 5,558,713 to Siegfried et al., which are incorporated hereinby reference in their entirety and in a manner consistent with thepresent invention. Such systems rely on relatively complex airconveyors, that may be susceptible to blockage and may not efficientlyaccommodate as wide a variety of particulate, powder and fibrousmaterials as other systems due to their relatively small passage sizes.Indeed, it has been found that the compressed air used in such pneumaticconveyors is often contaminated with oil that may cause blockage, SAPdegradation, and other problems. Such systems may also require arelatively long time to stabilize, leading to inefficiencies duringtransitional phases.

Other known SAP feeding systems are disadvantageous for a number ofreasons. First, the mixture of fiber and SAP still is subject to localconcentrations and shortages of SAP. Second, these feeding systemstypically can not be controlled accurately enough to provideconcentrations and shortages of SAP when they are desired. Third, suchfeeding systems can not be controlled to accurately provide reduced SAPamounts that are necessary during transitional phases, leading toimproperly loaded cores during those phases of operation.

These are just a few of the disadvantages of the prior art which thepreferred embodiments seek to address. The foregoing description ofcertain material, methods and systems with their attendant disadvantagesin no way is meant to infer that the present invention excludes suchmaterials, methods, and systems. Indeed, certain embodiments of theinvention may solve some of the aforementioned disadvantages, yetutilize the same or similar materials, methods and/or systems.

SUMMARY OF THE INVENTION

It would be desirable to provide an apparatus and method for formingtow-based absorbent structures, such as absorbent cores, that have onlya single tissue sheet that encases the entire absorbent core structure.It would further be desirable for such an apparatus and method to beefficient, easy to operate, and capable of operating at high linespeeds. In accordance with these and other features of variousembodiments of the invention, there is provided an apparatus and methodfor forming tow-based absorbent cores having a single casing sheet.

In accordance with one embodiment of the invention, there is provided anapparatus having a tow supply mechanism for providing tow material, aparticulate matter supply mechanism for providing particulate matter, acasing sheet supply mechanism for providing casing sheet material, and avacuum draw roll positioned to combined the tow, particulate matter andcasing sheet into and open core composite supply. The vacuum draw rollhas a foraminous center surface having a width defined by a first edgeand a second edge, and the vacuum draw roll is rotatable about a firstaxis. In addition, one or more angled surfaces are provided andpositioned to create one or more obtuse angles in the open corecomposite supply, and one or more folders are provided to further foldthe one or more obtuse angles in the open core composite supply to forma folded core composite supply.

In accordance with another embodiment of the invention, there isprovided an apparatus for forming absorbent structures having a singlecasing sheet, that has a casing sheet supply mechanism for providingcasing sheet material, a tow supply mechanism for providing towmaterial, and a particulate matter supply mechanism for providingparticulate matter. In this embodiment, the particulate matter supplymechanism is positioned to deposit the particulate matter onto thecasing sheet material. In this embodiment the apparatus has a vacuumdraw roll having a foraminous center surface, the foraminous centersurface having a width defined by a first edge and a second edge andbeing rotatable about a first axis. The vacuum draw roll is positionedafter the particulate matter supply mechanism to deposit the towmaterial onto the casing sheet material to form a open core compositesupply. In addition, this embodiment has one or more folders to fold theopen core composite supply into a folded core composite supply.

In various embodiments of the invention, the tow material is celluloseacetate, the particulate matter is superabsorbent particles, and thecasing sheet materials is tissue. In other embodiments, the particulatematter supply mechanism is a vibratory feeder and the tow supplymechanism is a tow forming jet.

In yet another embodiment, the casing sheet material has a center regionand first and second side regions located on opposite sides of thecenter region. The first side region extends from a first side of thecenter region to a first edge of the casing sheet material, and thesecond side region extends from a second side of the center region to asecond edge of the casing sheet material. In this embodiment, the casingsheet material is wider than the tow material, the tow material ispositioned adjacent to the center region of the casing sheet material inthe open core composite supply, and the one or more angled surfaces arepositioned to create a first obtuse angle at or near to the first sideof the center region, and a second obtuse angle at or near the secondside of the center region. Adhesive applicators may be used in these orother embodiments of the invention. In one embodiment, a first adhesiveapplicator is positioned before the vacuum draw roll to apply adhesiveto the center region of the casing sheet material. In anotherembodiment, a second adhesive applicator is operatively associated withthe one or more folders and positioned to apply adhesive to at least oneof the first and second side regions of the casing sheet material.

In still other embodiments, the angled surfaces may be operativelyassociated with the vacuum draw roll, and may comprise first and secondtapering surfaces that extend from respective edges of the foraminouscenter surface and taper inward from the center surface towards the axisabout which the vacuum draw roll rotates.

In another embodiment, the invention may have a break drum positionedbetween the vacuum draw roll and the one or more folders. The break drumis rotatable about a second axis and has a center surface that has awidth defined by a third edge and a fourth edge. The one or more angledsurfaces may, in one embodiment, be operatively associated with thebreak drum, and may be first and second tapering surfaces, thatextending from respective edges of the center surface of the break drumand taper inward from the center surface towards the axis about whichthe break drum rotates.

In another embodiment, the invention includes an open core compositesupply conveyor that is positioned to convey the open core compositesupply from the vacuum draw roll to the one or more folders. The opencore composite supply conveyor may have an arcuate region substantiallyadjacent to a sector of the vacuum draw roll.

In still another embodiment, the vacuum draw roll of the invention mayhave a rotatable outer drum upon which the foraminous center surface isdisposed, and an inner structure disposed at least partially within therotatable outer drum. In such an embodiment, the one or more angledsurfaces may be first and second tapering surfaces, located on the outerdrum, that extend from respective edges of the foraminous center surfaceand taper inward towards the first axis. The inner structure has avacuum chamber having one or more vacuum passages forming a vacuum zonesubadjacent at least a portion of the foraminous center surface. Thevacuum zone may have a leading edge and a trailing edge, as locatedrelative to the direction of rotation of the rotatable outer drum, and apositive air blow-off port located at the trailing edge of the vacuumzone.

In yet another embodiment, the foraminous center surface of the vacuumdraw roll may have a central vacuum region and first and second lateralvacuum regions, that are located between the central vacuum region andthe edges of the foraminous center surface. In this embodiment, thecentral vacuum region may be recessed. In this embodiment, the towmaterial may have an average width approximately equal to or less than awidth of the central vacuum region, and the central vacuum region may bepositioned to receive substantially the entire width of the towmaterial. The first and second lateral vacuum regions also may bepositioned to apply a vacuum to the casing sheet material.

In still another embodiment, the present invention provides a method forpreparing absorbent structures that have a single casing sheet. In oneembodiment, the method involves providing tow material, providingparticulate matter, providing casing sheet material, and forming an opencore composite supply by combining the tow material, the particulatematter and the casing sheet material on a vacuum draw roll comprising aforaminous center surface, the foraminous center surface having a widthdefined by a first edge and a second edge and being rotatable about afirst axis. This method also includes creating one or more obtuse anglesin the open core composite supply using one or more angled surfaces and,forming a folded core composite supply by folding flat the one or moreobtuse angles in the open core composite supply. In one embodiment ofthe method, the open core composite supply may be formed at the sametime that the one or more obtuse angles are formed in it. In variousother embodiments the method may further employ the various embodimentsof the apparatus described immediately above.

These and other features of the invention will be readily apparent fromthe Detailed Description that follows, along with reference to thedrawings appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a diaper-type absorbent garment, shown with theeffects of elastics removed for clarity;

FIG. 2 is a cross-sectional view of the garment of FIG. 1, as viewedfrom reference line 1—1;

FIG. 3 is a partially cut away side view of a system for dry formingabsorbent cores and other structures and machinery according to apreferred embodiment of the present invention, shown in operation and inrelation to a portion of an absorbent garment manufacturing line;

FIG. 4 is a partially cut away view of a feed tray according to apreferred embodiment of the present invention, shown at one end of itsrange of movement and showing the other end of its range of movement indashed lines;

FIG. 5A is a cut away view of a portion of a feed tray according to apreferred embodiment of the present invention;

FIG. 5B is a cut away view of a portion of another feed tray accordingto a preferred embodiment of the present invention;

FIG. 6 is a partially cut away side view of a feed tray, motor and sideplates according to a preferred embodiment of the present invention;

FIG. 7 is an isometric view of the outlet portion of a feed trayaccording to a preferred embodiment of the present invention;

FIG. 8 is an isometric view of a combining drum according to a preferredembodiment of the present invention;

FIG. 9 is a sectional view of the vacuum surface of a combining drumaccording to a preferred embodiment of the present invention, shownoperating with the core composite adjacent the vacuum surface;

FIG. 10 is a partially exploded isometric view of another combining drumaccording to a preferred embodiment of the present invention;

FIG. 11 is an isometric view of yet another combining drum according toa preferred embodiment of the present invention;

FIG. 12 is a cross sectional view of a combining drum assembly accordingto a preferred embodiment of the present invention as viewed from adirection orthogonal to the rotating axis of the combining drum, and asseen from reference line 3—3 of FIG. 13;

FIG. 13 is a cross sectional view of the combining drum assembly of FIG.12, as seen from reference line 2—2;

FIG. 14 is a partially cut away view of the combining drum assembly ofFIG. 12, shown with the outer drum partially removed;

FIG. 15 is an isometric view of the outlet portion of a feed trayaccording to another embodiment of the present invention;

FIG. 16A is a cross-sectional view of an embodiment of an absorbentgarment having a single casing sheet;

FIG. 16B is a cross-sectional view of another embodiment of an absorbentgarment having a single casing sheet;

FIG. 17 is a side view of an embodiment of a system for formingtow-based absorbent structures with a single casing sheet;

FIG. 18A is a cross-sectional view of an embodiment of an absorbent coreassembly during processing in the apparatus of FIG. 17 as viewed alongreference line 4—4 of FIG. 17, shown with the machinery removed forclarity;

FIG. 18B is a cross-sectional view of an embodiment of an absorbent coreassembly during processing in the apparatus of FIG. 17 as viewed alongreference line 5—5 of FIG. 17, shown with the machinery removed forclarity;

FIG. 18C is a cross-sectional view of an embodiment of an absorbent coreassembly during processing in the apparatus of FIG. 17 as viewed alongreference line 6—6 of FIG. 17, shown with the machinery removed forclarity;

FIG. 19 is a drawing of an embodiment of a tapered break roll of theembodiment of the apparatus of FIG. 17;

FIG. 20 is a drawing of an embodiment of angled surfaces and anuntapered break drum that may be used with the embodiment of FIG. 17;

FIG. 21 is a side view of another embodiment of a system for formingtow-based absorbent structures with a single casing sheet;

FIG. 22 is a side view of still another embodiment of a system forforming tow-based absorbent structures with a single casing sheet;

FIG. 23 is a top view of an embodiment of a stepped lay on roll that maybe used with a tapered vacuum draw roll in a system for formingtow-based absorbent structures with a single casing sheet;

FIG. 24 is an isometric view of an embodiment of a tapered vacuum drawroll that may be used in a system for forming tow-based absorbentstructures with a single casing sheet;

FIG. 25 is a cut away side view of the embodiment of a tapered combiningdrum of FIG. 24;

FIG. 26 is a partially cut away front view of the embodiment of atapered combining drum of FIG. 24;

FIG. 27 is a partially cut away front view detail drawing of theembodiment of a tapered combining drum of FIG. 24;

FIG. 28 is a side view of another embodiment of a system for formingtow-based absorbent structures with a single casing sheet;

FIG. 29 is a side view of yet another embodiment of a system for formingtow-based absorbent structures with a single casing sheet; and,

FIG. 30 is a side view of yet another embodiment of a system for formingtow-based absorbent structures with a single casing sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, the term “absorbent garment” or “garment” refers togarments that absorb and contain exudates, and more specifically, refersto garments that are placed against or in proximity to the body of thewearer to absorb and contain the various exudates discharged from thebody. A non-exhaustive list of examples of absorbent garments includesdiapers, diaper covers, disposable diapers, training pants, femininehygiene products and adult incontinence products. The term garmentincludes all variations of absorbent garments, including disposableabsorbent garments that are intended to be discarded or partiallydiscarded after a single use (i.e., they are not intended to belaundered or otherwise restored or reused) and unitary disposableabsorbent garments that have essentially a single structure (i.e., donot require separate manipulative parts such as a diaper cover andinsert). As used herein, the term “diaper” refers to an absorbentgarment generally worn by infants and incontinent persons about thelower torso.

The claims are intended to cover all of the foregoing classes ofabsorbent garments, without limitation, whether disposable, unitary orotherwise. The invention will also be understood to encompass, withoutlimitation, all other types of absorbent structure that may comprise anabsorbent core, whether described herein or not. Preferably, theabsorbent core or the garment is thin in order to improve the comfortand appearance of a garment. The importance of thin, comfortablegarments is disclosed, for example, in U.S. Pat. No. 5,098,423 toPieniak et al., which is incorporated herein by reference in itsentirety and in a manner consistent with the present invention.

Absorbent garments and diapers may have a number of differentconstructions. In each of these constructions it is generally the casethat an absorbent core is disposed between a liquid pervious,body-facing topsheet, and a liquid impervious, exterior facingbacksheet. In some cases, one or both of the topsheet and backsheet maybe shaped to form a pant-like garment. In other cases, the topsheet,backsheet and absorbent core may be formed as a discrete assembly thatis placed on a main chassis layer and the chassis layer is shaped toform a pant-like garment. The garment may be provided to the consumer inthe fully assembled pant-like shape, or may be partially pant-like andrequire the consumer to take the final steps necessary to form the finalpant-like shape. In the case of training pant-type garments and mostadult incontinent products, the garment is provided fully formed withfactory-made side seams and the garment is donned by pulling it up thewearer's legs. In the case of diapers, a caregiver usually wraps thediaper around the wearer's waist and joins the side seams manually byattaching one or more adhesive or mechanical tabs, thereby forming apant-like structure. For clarity, the present invention is describedherein only with reference to a diaper-type garment in which thetopsheet, backsheet and absorbent core are assembled into a structurethat forms a pant-like garment when secured on a wearer using fasteningdevices, although the invention may be used with other constructions.

Throughout this description, the expressions “upper layer,” “lowerlayer,” “above” and “below,” which refer to the various componentsincluded in the absorbent garments of the invention (including thelayers surrounding the absorbent core units), as well as the depictionin the drawings of certain layers or materials that are “above” or“below” one another, are used merely to describe the spatialrelationship between the respective components. The upper layer orcomponent “above” the other component need not always remain verticallyabove the core or component, and the lower layer or component “below”the other component need not always remain vertically below the core orcomponent. Indeed, embodiments of the invention include variousconfigurations whereby the core may be folded in such a manner that theupper layer ultimately becomes the vertically highest and verticallylowest layer at the same time. Other configurations are contemplatedwithin the context of the present invention.

The term “component” can refer, but is not limited, to designatedselected regions, such as edges, corners, sides or the like; structuralmembers, such as elastic strips, absorbent pads, stretchable layers orpanels, layers of material, or the like; or a graphic, embossed pattern,or the like.

Throughout this description, the term “disposed” and the expressions“disposed on,” “disposing on,” “disposed in,” “disposed between” andvariations thereof (e.g., a description of the article being “disposed”is interposed between the words “disposed” and “on”) are intended tomean that one element can be integral with another element, or that oneelement can be a separate structure bonded to or placed with or placednear another element. Thus, a component that is “disposed on” an elementof the absorbent garment can be formed or applied directly or indirectlyto a surface of the element, formed or applied between layers of amultiple layer element, formed or applied to a substrate that is placedwith or near the element, formed or applied within a layer of theelement or another substrate, or other variations or combinationsthereof.

Throughout this description, the terms “top sheet” and “back sheet”denote the relationship of these materials or layers with respect to theabsorbent core. It is understood that additional layers may be presentbetween the absorbent core and the top sheet and back sheet, and thatadditional layers and other materials may be present on the sideopposite the absorbent core of either the top sheet or the back sheet.

Throughout this description, the expression “fibrous material” denotesany fibrous material that may be used in an absorbent garment, includingwithout limitation, various hardwood and softwood fluff pulps, tissues,cottons, and any other fibrous materials described herein. “Fibrousmaterial” used in the context of the present invention is not intendedto limit the invention to any particular type of fibrous material.

Throughout this description, the expression “tow fibers” relates ingeneral to any continuous fiber. Tow fibers typically are used in themanufacture of staple fibers, and preferably are comprised of syntheticthermoplastic polymers. Usually, numerous filaments are produced by meltextrusion of the molten polymer through a multi-orifice spinneret duringmanufacture of staple fibers from synthetic thermoplastic polymers inorder that reasonably high productivity may be achieved. The groups offilaments from a plurality of spinnerets typically are combined into atow which is then subjected to a drawing operation to impart the desiredphysical properties to the filaments comprising the tow.

A preferred embodiment of the present invention comprises a disposableabsorbent garment 10 of the diaper type, such as shown, for example, inFIG. 1. It should be understood, however, that the present invention isapplicable to other types of absorbent garments. With reference to FIG.1, the diaper 10 according to a first preferred embodiment is shown in arelaxed condition with the effects of the elastics removed for purposesof clarity in the description. The diaper 10 has a generally hourglassshape and can generally be defined in terms of a front waist region 22,a back waist region 24, and a crotch region 26. Those skilled in the artwill recognize that “front” and “back” are relative terms, and theseregions may be transposed without departing from the scope of thepresent invention. Alternatively, the diaper can be configured in agenerally rectangular shape or in a “T” shape. A pair of leg openings 28a, 28 b extend along at least a portion of the crotch region 26. Thediaper preferably comprises a topsheet 2, a backsheet 4, which may besubstantially coterminous with the topsheet 2, and an absorbent core 6disposed between at least a portion of the topsheet 2 and backsheet 4.One or more pairs of leg elastics 8 (three pairs are shown in FIG. 1)may be disposed to extend adjacent to leg openings 28 a, 28 b,respectively. Of course, in other embodiments, the leg elastics 8 may beomitted altogether.

The diaper may further include a front waist elastic system 30 a, a backwaist elastic system 30 b, a fastening system 32 (e.g., tape or othersuitable mechanical fastener) and a waste containment system in the formof waste containment flaps 12 (also known as standing leg gathers).Waste containment flaps 12 (FIG. 2) preferably extend from the frontwaist region 22 to the back waist region 24 along opposite sides of alongitudinal center line or axial center line 60 of the diaper 10, oralternatively only along a portion thereof. The front waist region 22and rear waist region 24 may include ear portions 38,40 extendingoutwardly from the leg openings 28 a, 28 b.

A variety of backsheet and topsheet constructions and materials areavailable and known in the art, and the invention is not intended to belimited to any specific materials or constructions of these components.The backsheet 4 is of any suitable pliable liquid-impervious materialknown in the art. Typical backsheet materials include films ofpolyethylene, polypropylene, polyester, nylon, and polyvinyl chlorideand blends of these materials. For example, the backsheet can be apigmented polyethylene film having a thickness in the range of 0.02-0.04mm. The moisture-pervious topsheet 2 can be any suitable relativelyliquid-pervious material known in the art that permits passage of liquidtherethrough. Non-woven topsheet materials are exemplary because suchmaterials readily allow the passage of liquids to the underlyingabsorbent core 6. Examples of suitable topsheet materials includenon-woven spunbond or carded webs of polypropylene, polyethylene, nylon,polyester and blends of these materials.

The backsheet 4 and the topsheet 2 preferably are “associated” with oneanother. The term “associated” encompasses configurations whereby thetopsheet 2 is directly joined to the backsheet 4 by affixing thetopsheet 2 directly to the backsheet 4, and configurations whereby thetopsheet 2 is indirectly joined to the backsheet 4 by affixing thetopsheet 2 to intermediate members which in turn are affixed to thebacksheet 4. While the backsheet 4 and topsheet 2 in the preferredembodiment have substantially the same dimensions, they may also havedifferent dimensions.

In addition, the backsheet 4 may be covered with a fibrous, nonwovenfabric such as is disclosed for example in U.S. Pat. No. 4,646,362,which is incorporated herein by reference in its entirety and in amanner consistent with the present invention. Materials for such afibrous outer liner include a spun-bonded nonwoven web of syntheticfibers such as polypropylene, polyethylene or polyester fibers; anonwoven web of cellulostic fibers, textile fibers such as rayon fibers,cotton and the like, or a blend of cellulostic and textile fibers; aspun-bonded nonwoven web of synthetic fibers such as polypropylene;polyethylene or polyester fibers mixed with cellulostic, pulp fibers, ortextile fibers; or melt blown thermoplastic fibers, such as macro fibersor micro fibers of polypropylene, polyethylene, polyester or otherthermoplastic materials or mixtures of such thermoplastic macro fibersor micro fibers with cellulostic, pulp or textile fibers.

The backsheet 4 may comprise multiple panels, such as three panelswherein a central poly backsheet panel is positioned adjacent theabsorbent core while outboard non-woven breathable side backsheet panelsare attached to the side edges of the central poly backsheet panel. Thebacksheet may also be formed from microporous poly coverstock for addedbreathability. In other embodiments, the backsheet may be a laminate ofseveral sheets. The backsheet may further be treated to render ithydrophilic or hydrophobic, and may have one or more visual indicatorsassociated with it, such as labels indicating the front or back of thediaper or other characters or colorations. The present invention is notlimited to any particular backsheet 4 material or construction.

The topsheet 2 may be formed from one or more panels of material and maycomprise a laminated sheet construction. In the embodiment of FIG. 1,the topsheet comprises three separate portions or panels. A three-paneltopsheet may comprise a central topsheet panel 2 a (FIG. 2) thatpreferably is formed from a liquid-pervious material that is eitherhydrophobic or hydrophilic. The central topsheet panel 2 a may be madefrom any number of materials, including synthetic fibers (e.g.,polypropylene or polyester fibers), natural fibers (e.g., wood orcellulose), apertured plastic films, reticulated foams and porous foamsto name a few. One preferred material for a central topsheet panel 2 ais a cover stock of single ply non-woven material which may be made ofcarded fibers, either adhesively or thermally bonded, perforated plasticfilm, spunbonded fibers, or water entangled fibers, which generallyweigh from 0.3-0.7 oz./yd² and have appropriate and effective machinedirection and cross-machine direction strength suitable for use as ababy diaper cover stock material, as are known in the art. The centraltopsheet panel 2 a preferably extends from substantially the front waistregion 22 to the back waist region 24 or a portion thereof.

The second and third topsheet panels 2 b, 2 c in this embodiment may bepositioned laterally outside of the central topsheet panel 2 a. Theouter topsheet panels 2 b, 2 c preferably are substantiallyliquid-impervious and hydrophobic, preferably at least in the crotcharea. The outer edges of the outer topsheet panels may substantiallyfollow the corresponding outer perimeter of the backsheet 4. Thematerial for the outer topsheet portions or panels preferably ispolypropylene and can be woven, non-woven, spunbonded, carded or thelike, depending on the application.

An inner region 34 (FIG. 2) of the outer topsheet portions or panels 2b, 2 c preferably is attached by, e.g., an adhesive, to the outer edges36 of the inner topsheet portion or panel 2 a. At the point ofconnection with the outer edges 36 of the inner topsheet portion orpanel 2 a, the inner regions 34 of the outer topsheet portions or panels2 b, 2 c extend upwardly to form waste containment flaps 12. The wastecontainment flaps 12 may be formed of the same material as the outertopsheet portions or panels 2 b, 2 c, as in the embodiment shown. Thewaste containment flaps 12 may also be formed from separate elasticizedstrips of material that are associated with the topsheet, backsheet orboth, or otherwise integrated into the garment.

The waste containment flaps 12 may be treated with a suitable surfactantto modify their hydrophobicity/hydrophilicity or imbue them with skinwellness products as desired. The central topsheet portion or panel 2 amay extend past the connection point with the waste containment flaps 12and even extend to the periphery of the backsheet. Still further, thecentral topsheet portion or panel 2 a could extend fully between theouter topsheet portions or panels 2 b, 2 c and even beyond so that theouter edges 36 of the central topsheet portion or panel 2 a arecoextensive with and sandwiched between the outer topsheet portions orpanels 2 b, 2 c and the backsheet 4.

The waste containment flaps 12 each preferably includes a portion thatfolds over onto itself to form an enclosure. One or more elastic members14 (FIG. 2) may be secured in the enclosure in a stretched condition. Ashas been known at least as long the disclosure of Tetsujiro, JapanesePatent document 40-11543, when the flap elastic 14 attempts to assumethe relaxed, unstretched condition, the waste containment flaps 12 riseabove the surface of the central topsheet portion or panel 2 a. Variousother configurations of topsheets 2 and waste containment systems, suchas flaps 12, are known in the art, and the present invention is notintended to be limited to any particular design for these components.

The waist elastics 30 a, 30 b (FIG. 1) may be similar structures ordifferent to impart similar or different elastic characteristics to thefront and back waist portions 22, 24 of the diaper. In general, thewaist elastics may comprise elastically extensible foam stripspositioned at the front and back waist sections 22, 24. The foam stripsare preferably about 0.50 inches to about 1.50 inches wide and about 3inches to about 6 inches long. The foam strips are preferably positionedbetween the topsheet portions or panels and the backsheet 4.Alternatively, a plurality of elastic strands may be employed as waistelastics rather than foam strips. The foam strips are preferablypolyurethane, but could be any other suitable material that preferablydecreases waist band roll over, reduces leakage over the waist ends ofthe absorbent garment, and generally improves comfort and fit. The frontand back waist foam strips 30 a, 30 b are stretched 50-150%, preferably100% before being adhesively secured between the backsheet 4 andtopsheet 2. Waist elastics are known in the art, and the presentinvention is not limited to the use of a particular waist elasticsystem, or to the inclusion of waist elastics at all.

Each leg opening 28 a, 28 b may be provided with a leg elasticcontainment system 8, sometimes referred to as conventional leg gathers.In a preferred embodiment, three strands of elastic threads arepositioned to extend adjacent the leg openings 28 a, 28 b between theouter topsheet portions or panels 2 b, 2 c and the backsheet 4 theselection of appropriate elastics and the construction of leg elasticcontainment systems is known in the art. For example, the leg elastics 8may be ultrasonically bonded, heat/pressure sealed using a variety ofbonding patterns, or glued to the diaper 10.

Various commercially available materials may be used for the legelastics 8 and elastic members 14, such as natural rubber, butyl rubberor other synthetic rubber, urethane, elastomeric materials such asspandex, which is marketed under various names, including LYCRA(DuPont), GLOSPAN (Globe) and SYSTEM 7000 (Fulflex), and so on. Thepresent invention is not limited to any particular elastic.

The fastening system of the diaper 10 may be attached to the back waistregion 24, and preferably comprises tape tabs or mechanical fasteners32. However, any fastening known in the art will be acceptable.Moreover, the fastening system may include a reinforcement patch belowthe front waist portion so that the diaper may be checked for soilingwithout compromising the ability to reuse the fastener. Alternatively,other diaper fastening systems are also possible, including safety pins,buttons, and snaps. Fastening systems are known in the art, and thepresent invention is not limited to using any particular fastening, andmay be constructed without any fastening system at all, such as intraining pant-type garments.

As stated previously, the invention has been described in connectionwith a diaper. The invention, however, is not intended to be limited toapplication only in diapers. Specifically, the present invention may bereadily adapted for use in other absorbent garments besides diapers,including, but not limited to, training pants, feminine hygiene productsand adult incontinence products.

The underlying structure beneath the topsheet 2 may include, dependingon the diaper construction, various combinations of elements, but ineach embodiment, it is contemplated that the absorbent garment willpreferably include an absorbent core 6. For example, an additional layer20 may be disposed between the topsheet 2 and absorbent core 6, as shownin FIG. 2, and/or other additional layers may be disposed between theselayers, or between absorbent core 6 and backsheet 4. The additionallayer 20 or layers may comprise any useful layer known in the art ordeveloped hereafter, such as a fluid acquisition layer, a distributionlayer, an additional fibrous layer optionally containing SAP, a wickinglayer, a storage layer, or combinations and fragments of these layers.Such layers may be provided to assist with transferring fluids to theabsorbent core 6, handling fluid surges, preventing rewet, containingabsorbent material, improving core stability, or for other purposes.Skilled artisans are familiar with the various additional layers thatmay be included in an absorbent article, and the present invention isnot intended to be limited to any particular type of materials used forthose layers. Rather, the invention encompasses all types of wickinglayers, all types of distribution layers, etc., to the extent that typeof layer 20 is utilized.

The dimensions of additional layer(s) 20 may be the same as or differentfrom the dimensions of the absorbent core 6 and/or topsheet 2 andbacksheet 4. It is preferred that additional layer(s) 20 have a width inthe lateral direction (102) of anywhere from about 10 mm to about 100mm, and preferably from about 25 mm to about 80 mm.

Although the absorbent core 6 depicted in FIG. 1 has a substantiallyrectangular shape as viewed in the plan view, other shapes may be used,such as a “T” shape or an hourglass shape. The absorbent core 6 mayextend into either or both of the front and back waist regions 24, 22.The shape and construction of the absorbent core 6 may be selected toprovide the greatest absorbency in target areas where body fluids aremost likely to strike the diaper 10, which is often referred to as zonedabsorbency. The absorbent core 6 may also comprise a number of layers ofsimilar or different construction. The absorbent core may be associatedwith the topsheet 2, backsheet 4, or any other suitable part of thegarment 10 by any method known in the art, in order to fix the absorbentcore 6 in place.

Generally, in a preferred embodiment, the absorbent core 6 comprisesparticles of super absorbent polymer distributed within a fibrousstructure. Additional fibrous or particulate additives may be disposedwithin the absorbent core 6 to add to the core's strength and SAPefficiency or to otherwise enhance the performance of the garment. Theabsorbent core 6 may be partially or wholly surrounded by a tissue layer16, 18, and other additional layers 20 may be added to provide furtherbenefits. The various components of the absorbent core 6 are nowdescribed in greater detail.

Certain fibrous materials preferably are used to form the fibrousstructure of the absorbent core 6 of the present invention. Thesefibrous materials maintain high SAP efficiencies when the SAP weightconcentration is in the range of about 50-95%, more preferably about65-95%, and most preferably about 80-95% (as measured in the absence oftissue, glue or other core components). For example, the fibrousstructure of the absorbent core 6 may be made with cellulose acetatefibers, polypropylene fibers, rayon fibers, Courtauld's LYOCELL fibers,polyacrylonitrile fibers, surface-modified (hydrophilic) polyesterfibers, surface-modified polyolefin/polyester bicomponent fibers,surface-modified polyester/polyester bicomponent fibers, cotton fibers,blends of the foregoing materials, and the like.

Of the foregoing, cellulose acetate or polyolefinic (e.g., polypropyleneor polyethylene) tow fibers are the most preferred materials for use asthe fibrous structure. In addition, rayon, Courtauld's LYOCELL,polyacrylonitrile, cotton fibers and cotton linters have similarproperties to cellulose acetate and are alternatively preferred. Theremaining fibers, surface-modified polyolefin/polyester bicomponentfibers, and surface-modified polyester/polyester bicomponent fibers arealso believed to be effective as a fibrous structure or as fibrousadditives. Of course, other fibers may also be used. To maintain highSAP concentrations, the weight concentration of fibrous material formingthe absorbent core 6 of the invention preferably is about 5-50%, morepreferably about 5-35%, and most preferably about 5-20% (as measured inthe absence of tissue, glue or other core components). Most preferably,the absorbent core 6 comprises from about 80-95% SAP and from about5-20% fibrous structure material chosen from the foregoing group.

In accordance with the present invention, improved absorbent articlesare advantageously based upon continuous crimped filament tow, andaccordingly, the central fibrous structure of the core 6 isadvantageously prepared therefrom. This fiber structure has highstructural integrity, and as such, is distinct from a matrix ofdiscontinuous fibers, often described as fluff or fluff pulp, that iscommonly used in the prior art. The high structural integrity enablesthe production of stronger webs than those formed from discontinuousfibers, which in turn are believed to enable the production of thinnerabsorbent pads. In addition, the use of such fibers enables theproduction of ultra low density absorbent cores, when compared toabsorbent cores prepared by dispersing SAP particles in fluff. Thereduction in density is largely attributable to the reduced weight ofthe fibrous structure. Absorbent cores 6 constructed from a blend ofsuch materials and SAP are referred to herein as “tow/SAP” cores or“tow-based” cores.

Beneficially, cellulose ester tow is used to form the fibrous structure.Non-limiting examples of suitable cellulose esters include celluloseacetate, cellulose propionate, cellulose butyrate, cellulose caproate,cellulose caprylate, cellulose stearate, highly acetylated derivativesthereof such as cellulose diacetate, cellulose triacetate and cellulosetricaproate, and mixtures thereof such as cellulose acetate butyrate. Asuitable cellulose ester preferably will have the ability to absorbmoisture, is biodegradable, and is influenced not only by thesubstituent groups but also by the degree of substitution. Therelationship between substituent groups, degree of substitution andbiodegradability is discussed in W. G. Glasser et al, BIOTECHNOLOGYPROGRESS, vol. 10, pp. 214-219 (1994), the disclosure of which isincorporated herein by reference in its entirety.

Alternatively, a polyolefinic fiber tow may be used beneficially withthe present invention. Polyolefinic fibers offer certain advantages, forexample, they are typically available in a wider denier range than othermaterials and they are thermoplastic and thus can be embossed. Inaddition, polyolefinic fibers have a relatively high resiliency, makingmore able to spring back after being placed under pressure. Suchresiliency is beneficial because it creates a buffer between the wearerand the wetted SAP that reduces rewet values and makes the garment morecomfortable.

Typically, the denier per fiber (dpf) of the tow fiber will be in therange of about 1 to 30, preferably about 7 to 15, and most preferablyabout 10. For the same weight product, filaments of lower dpf mayprovide increased surface area and increased moisture absorption. Totaldenier of the tow may vary within the range of about 5,000 to 80,000,depending upon the process and material used, and is preferably about30,000. Lower total deniers provide a more open structure that allowsfree transfer of fluid, while higher total deniers tend to obstruct themovement of fluid and rely more on capillary fluid conveyance. The totaldenier should not be excessively reduced, however, as this may result ininadequate core strength, reduced resiliency (leading to increasedrewet), and reduced comfort. The foregoing dpfs and total deniers arebeneficial for cellulose acetate tows and polyolefinic fiber tows. Ofcourse, other dpfs and total deniers may be selected according to theparticular material used for the fiber. The fibers may have a circular,ovate, rectilinear, or any other cross section. In one embodiment, thefibers have a tri-lobal cross section with an area of about 3.36×10⁻⁶cm². Such a cross-sectional shape may provide improved bendingstiffness, increased wicking, or other beneficial properties.

Tow typically is provided as a relatively dense matrix of fibers, and itis often desirable to “open” (also known as “fluffing” or “blooming”)the tow into a more voluminous cotton-like matrix. Various methods anddevices for opening tow are known in the art. For example, U.S. Pat. No.4,468,845 to Harris discloses a tow forming jet having a jet portionthat injects gasses into the tow that cause the tow to separate when thegasses escape, and a bustle portion that collects the tow into acotton-like mass, thereby essentially completing the blooming operation.Another device, disclosed in U.S. Pat. No. 6,253,431, operates without adancer (i.e. tension plate). These or any other tow opening device maybe used with the present invention.

Tow having crimped filaments may be used with the present invention, asthe crimps aid with opening the tow. The separation of filamentsresulting from the opening process advantageously results in increasedavailable filament surface area for superabsorbent materialimmobilization and increased moisture absorption. Gel blocking also maybe reduced by using crimped tow in the absorbent core 6. As thereforemay be understood, more crimp is typically better, with an excess ofabout 20 crimps per inch being usually preferred. Continuous filamentcellulose ester tow having crimped filaments with about 25 to 40 crimpsper inch is commercially available from Hoechst Celanese Corporation ofCharlotte, N.C. However, it should be understood that uncrimped towfilaments or filaments having relatively few crimps also may be usedwith the present invention, and may provide a cost advantage withoutsubstantially reducing the performance of the garment.

If desired, an absorbent core 6 of multiple layer thickness may beprovided. To this end, the tow may be, for example, lapped orcrosslapped in accordance with conventional procedures. In this way, asuperabsorbent, absorptive material of a desired weight and/or thicknessmay be provided. The specific weight or thickness will depend uponfactors including the particular end use.

Any superabsorbent polymer (SAP) now known or later discovered may beused in the absorbent core 6, so long as it is capable of absorbingliquids. In addition, the SAP may be omitted from the core 6 in somecircumstances, such as when a swim garment is produced. Useful SAPmaterials are those that generally are water-insoluble butwater-swellable polymeric substances capable of absorbing water in anamount that is at least ten times the weight of the substance in its dryform. In one type of SAP, the particles or fibers may be describedchemically as having a back bone of natural or synthetic polymers withhydrophilic groups or polymers containing hydrophilic groups beingchemically bonded to the back bone or in intimate admixture therewith.Included in this class of materials are such modified polymers as sodiumneutralized cross-linked polyacrylates and polysaccharides including,for example, cellulose and starch and regenerated cellulose which aremodified to be carboxylated, phosphonoalkylated, sulphoxylated orphosphorylated, causing the SAP to be highly hydrophilic. Also includedare water swellable polymers of water soluble acrylic or vinyl monomerscrosslinked with a polyfunctional reactant. Such modified polymers mayalso be crosslinked to reduce their water-solubility, and suchcross-linked SAPs have been found to provide superior performance insome absorbent cores. A more detailed recitation of superabsorbentpolymers is found in U.S. Pat. No. 4,990,541 to Nielsen, the disclosureof which is incorporated herein by reference in its entirety. The SAP ispreferably selected to provide high absorbency performance for theparticular application. The measure of the SAP's absorbency performancemay be evaluated in a number of ways, as will be understood by thoseskilled in the art. For example, it may be desirable, in some cases, toprovide a SAP having a high measure of saline flow conductivity (SFC),as is described in U.S. Pat. No. 5,562,646 to Goldman et. al, which isincorporated herein by reference in its entirety and in a mannerconsistent with the present invention. However, the present invention isalso suitable for providing a low saline flow conductivity, which alsomay provide certain benefits, such as higher capacity and absorbencyunder load. Of course, the SAP may be selected to provide otherproperties or combinations of properties as well.

Commercially available SAPs include a starch modified superabsorbentpolymer available under the trade name SANWET from BASF of Portsmouth,Va. SANWET is a starch grafted polyacrylate sodium salt. Othercommercially available SAPs include a superabsorbent derived frompolypropenoic acid, available under the trade name DRYTECH 520SUPERABSORBENT POLYMER from The Dow Chemical Company, Midland Mich.;AQUA KEEP manufactured by Seitetsu Kagaku Co., Ltd.; ARASORBmanufactured by Arakawa Chemical (U.S.A.) Inc.; and FAVOR manufacturedby Stockhausen Inc. Still other commercially available SAPs includeSA55SX, available from Sumitomo Chemical Co. Ltd. of Osaka, Japan, and3900, 8400 and 8600 provided by BASF of Portsmouth, Va.

The SAP may be provided in any particle size, and suitable particlesizes vary greatly depending on the ultimate properties desired.Preferably, a fine particulate rather than a coarse particulate, is usedin the invention, and preferably a fine particulate that passes throughan about 200 mesh screen is used.

It has been known to prepare absorbent cores comprised of celluloseacetate tow or other polymeric fibers and SAP, as described in U.S.Statutory Invention Registration H1565, and U.S. Pat. Nos. 5,436,066,and 5,350,370, the disclosures of each of which are incorporated byreference herein in their entirety and in a manner consistent with thepresent invention. It was conventional to add tackifying agents,specific size fibers, or specific fibers in combination with fluff, inorder to prepare the absorbent core and immobilize the SAP particles.These additional materials may add to density of the core, or otherwiseadversely affect the overall performance of the absorbent garment madetherefrom. Thus, the use of such additives (or any other additives,adhesives, bonding agents or the like) should be controlled to minimizeany negative effects caused by their inclusion.

The total basis weight of the absorbent core 6 including fibrousmaterials, SAP, tissue, additional layers, and additives, typically maybe anywhere from about 50 grams per square meter (gsm) to about 1,000gsm. The most preferred total basis weight of the absorbent core 6 isabout 250 gsm to about 700 gsm.

Additional particles or fibrous additives may be added to the absorbentcore 6 to help maintain high SAP efficiency, to reduce the cost of thegarment, or to provide other benefits. Fibrous additives may beintroduced as part of the supply of unopened tow or may be added to towafter it has been opened. In a preferred embodiment, particulateadditives generally may be added to the tow after it has been opened toallow practical manufacture of the tow and to prevent losses of theparticulate additives during processing.

In one embodiment, about 1-10%, and preferably about 5%, by weight ofthermally bondable synthetic fibers may be added to the absorbent core 6to impart additional wet strength to the laminate. These additive fibersmay improve the stability of the core during use of the diaper. Thepreferred synthetic fibers for such an embodiment arepolyolefin/polyester fibers and polyester/polyester bicomponent fibers.

In another embodiment, the fibrous structure may comprise a combinationof preferred tow materials or a combination of a tow material and afluff pulp material, such as a blend of cellulose ester and conventionalsoft or hard wood fibers. Such combinations may be useful to maintainthe improved SAP efficiency available from the crimped filamenttow-based fibrous structure while providing additional benefits. Forexample, it has been discovered that an absorbent core 6 having a 150g/m² composite comprised of 80% SAP, 10% cellulose acetate, and 10%conventional fluff pulp has a SAP efficiency of about 85%, whereas anabsorbent core 6 comprised of 80% SAP and 20% fluff pulp SAP has anefficiency of about 70%.

The particulate additives that may be added to the absorbent core 6preferably are insoluble, hydrophilic polymers with particle diametersof 100 μm or less. These particulate additives may be chosen to impartoptimal separation of the SAP particles. Examples of preferredparticulate additive materials include, but are not limited to, potato,corn, wheat, and rice starches. Partially cooked or chemically modified(i.e., modifying hydrophobicity, hydrophilicity, softness, and hardness)starches can also be effective. Most preferably, the particulateadditives comprise partially cooked corn or wheat starch because in thisstate, the corn or wheat are rendered larger than uncooked starch and inthe cooked state remain harder than even swollen SAP. In any event,regardless of the particulate additive chosen, one of the many importantcriteria is to use particulate additives that are hard hydrophilicmaterials relative to swollen SAP or which are organic or inorganicpolymeric materials about 100 microns in diameter. Fibrous andparticulate additives can be used together in these absorbent laminates.Examples of SAP/particulate and SAP/fiber/particulate additives includethose described in, for example, U.S. Pat. No. 6,068,620.

Other particulate or powdered additives also may be deposited within theabsorbent core 6 to provide odor control, skin wellness, and improvedappearance. For example, zeolites, sodium bicarbonate and perfumes maybe added to reduce or mask odors, and titanium dioxide or othercolor-imbuing compounds may be added to provide the absorbent core 6with a more pleasant color.

The absorbent core 6 preferably comprises a tissue wrapping that atleast partially encloses the preferred blended tow and SAP, such asdisclosed in U.S. Pat. No. 6,068,620. The tissue wrapping is useful, forexample, for containing the SAP within the absorbent core 6 andproviding strength to the core during manufacturing and use. In apreferred embodiment, the tissue wrapping comprises first and secondtissue layers 16, 18 that encase the absorbent core 6, and mayoptionally also encase one or more additional layers 20. Preferably, thefirst tissue layer 16 is located generally between the topsheet 2 andthe absorbent core 6, and is hydrophilic and fluid pervious. It is alsopreferred that the second tissue layer 18 be located between thebacksheet 4 and the absorbent core 6 and be hydrophobic and fluidimpervious. The tissue wrapping may also comprise a single tissue layerthat has been folded to encase the absorbent core, and that may be zonetreated to render the portion that forms the lower tissue layer 18hydrophobic and fluid impervious. Embodiments having a single tissuelayer are described in more detail below, but generally may have all ofthe features described herein with reference to embodiments havingmultiple tissue layers. The tissue layers 16, 18 or the whole core 6 maybe crimped, folded, sealed or bonded to help contain the SAP particles.

In one embodiment, the tissue, fibrous structure and SAP of theabsorbent core may be adhesively or thermally bonded to improve theabsorbent core's wet strength and core stability. This may, in somecases, result in slower than adequate rates of absorption and poor SAPefficiency. In another embodiment the SAP and fibrous structure may behydrogen bonded to additional the tissue layers 16, 18. When a tow-basedfibrous structure having a high concentration of SAP is hydrogen bondedto first and second tissue layers 16, 18 to form an absorbent core 6,the SAP efficiency is not impaired, wet strength increases, and thefirst and second tissue layers 16, 18 add stability to the core 6 duringmanufacture. It has been found that when the fibrous structure of theabsorbent core 6 is hydrogen bonded using water to the tissue layers 16,18, unexpectedly good “core utilization” is realized. “Core utilization”is the percentage of the total capacity of a core that can be absorbedin a demand absorbency test. This unexpected performance improvement isbelieved to be the result of the beneficial liquid distribution providedby the intimate bond between the fibers of the fibrous structure and thetissue layers 16, 18.

In another preferred embodiment, the first and second tissue layers 16,18 are coated with adhesive prior to being placed on either side of theabsorbent core 6, thereby providing strength to the core and adhesivelyholding a portion of the SAP in place during use. The tissue layers 16,18 may be provided having a width greater than the fibrous structure ofthe absorbent core 6, and the portions of the tissue layers 16, 18extending past either side of the fibrous structure of the core 6 may bebonded to one another to provide further SAP retention capability. Instill another embodiment, if the fibrous structure contains about 1-5%by weight thermally bondable synthetic fibers, bonding to the tissuelayers 16, 18 may be achieved using thermal bonds.

The absorbent core 6 of the present invention may flat or folded when itis fixed in place between the topsheet 2 and backsheet 4. Folded coresmay provide additional performance benefits, such as improved fluidredistribution, greater SAP efficiency, and so on. The absorbent core 6can be folded in any suitable manner, including any and all of thosedisclosed in U.S. Pat. No. 6,068,620. Those skilled in the art willappreciate that the absorbent core 6 can be folded such that theadjacent sides are touching one another, or so that channels are formedin certain areas. For example, the absorbent core 6 can be folded in theform of a “C” where the curled ends may be spaced apart to form achannel there between, and the lower edges of the curled ends may bedisposed adjacent the upper edges of the bottom portion of the foldedarticle. Alternatively, another absorbent material, or another absorbentcore 6 may be disposed in the space formed by the standard “C” fold. Thesame considerations may be given to embodiments having a “G” fold or a“U” fold where the spaces formed by these folds may be filled withanother absorbent material, another absorbent core 6, left open to formfluid handling channels, or the folds may be made tight enough so thatlittle or no space is formed. Other possible arrangements include a “Z”fold, and a pleated absorbent core 6, and other folded shapes, as willbe appreciated by those skilled in the art.

The absorbent core 6 preferably is formed using a dry process. Dryprocesses have numerous benefits over wet processes. For example, in wetprocesses, the core material is typically immersed in a fluid having asuperabsorbent particles mixed or suspended therein, and the corematerial may require additional drying steps and other steps that add tothe complexity and cost of the core forming process. In addition, wetprocesses often require the absorbent core to be manufactured off of themain assembly line. Dry processes typically have lower operating coststhan wet processes because the equipment used in dry processes istypically less complex and can run at higher line speeds. Further, dryforming processes may often be adapted for use directly on the line ofconventional diaper machines. A preferred embodiment of the presentinvention is particularly concerned with using a dry forming process tomanufacture absorbent cores having high concentrations of SAP andrelatively low basis weights, while overcoming or avoiding thedeficiencies of known dry forming processes and machines, as describedelsewhere herein.

One challenge with making absorbent cores having high concentrations ofSAP and relatively low basis weight fibrous structures, as describedabove, is to achieve the desired distribution of SAP within the core. Inmany cases it may be desirable to achieve a uniform distribution of SAPwithin the core to provide the absorbent garment with uniform absorptioncapability. In such a case, not only should the SAP be evenlydistributed along the length and width of the absorbent core, but italso should be properly distributed throughout the thickness of the coreto ensure that the SAP is not subject to gel blocking or otherinefficiencies during use. It also is desirable to provide a controlledamount of SAP to the core to prevent overuse of the SAP, which typicallyis relatively expensive. It may be further desirable to preciselycontrol the distribution of SAP to provide local regions of the corethat have greater SAP concentrations than others to provide zonedabsorbency. Such concentrations may be along one or more of theabsorbent core's length, width and thickness.

Referring now to FIG. 3, a preferred embodiment of an apparatus andmethod for dry forming composite cores is shown. In the preferredembodiment, a tow supply 302, which may be unopened or partially opened,is provided along a first path to enter a forming jet assembly 304. Thesupply of tow may comprise any material that is desired to be used asthe fibrous structure of the garment's absorbent core 6 and is suitablefor use in the process described herein, such as those that have beendescribed elsewhere herein. Those skilled in the art will appreciatethat if fibers, fluff, or pulp other than tow fibers are used, formingjet assembly 304 would be replaced by a suitable fiber or fluff formingapparatus, as are well known in the art. A preferred material for thetow supply 302 is a supply of cellulose acetate having a basis weight ofabout 50 g/m² to about 100 g/m², and more preferably of about 76 g/m².The tension, speed and path of the tow supply 302 may be adjusted by oneor more movable pulleys 306, guides (not shown) and/or festoons (notshown), as are known in the art.

The tow supply 302 enters the forming jet assembly 304 and is opened inpreparation for being incorporated into absorbent cores. The forming jetassembly 304 comprises a tow inlet 308 at one end into which the towsupply 302 is fed. One or more high velocity jets 310 of air or othergas are projected into the forming jet assembly to impinge upon the towsupply 302 to thereby separate the fibers and “bloom” or open the tow.Preferably, two jets 310 are used and each jet 310 is located proximalto the tow inlet 308 and on opposite sides of the tow supply 302. Eachof the jets 310 preferably comprises a flow of air moving at about 17.5cubic feet per minute through a slit-shaped port that has a length ofabout 3.94 inches and a width of about 0.003 inches. Similar devices foropening tow are known in the art, and disclosed, for example, in U.S.Pat. No. 5,331,976 to St. Pierre, which is incorporated herein byreference in its entirety and in a manner consistent with the presentinvention. Other devices and procedures for opening the tow supply 302may also be used with the present invention, as will be understood bythose skilled in the art.

The opened or “bloomed” tow 312 accumulates within the forming jetassembly 304 as it is being used, and the amount of opened tow 312 beingconsumed may be measured by a level meter 314 (also known as a“dancer”). The level meter 314 may be any suitable electromechanical,optical, or other type of device capable of measuring the amount ofopened tow 312 being consumed. In a preferred embodiment, the levelmeter 314 is a plate that is pivotally attached to a rotary positionsensor (such as a commonly known variable resistance or potentialdevice). As the level of opened tow 312 increases or decreases, theplate pivots up and down, thereby changing the output of the rotaryposition sensor. In a preferred embodiment, the level meter 314 is usedas part of a closed-loop feedback algorithm or an open-loop algorithm tometer the rate at which the tow supply 302 is fed into the forming jetassembly 304, and may be integrated into a control system 320.

The control system 320 may comprise any electrical control apparatusthat may be configured to control one or more variables based on themeasurement of one or more inputs. Although the control system 320 isreferred to herein in the singular, it should be understood that anumber of independent control systems 320 may be used for various partsof the machinery, and these various systems are referred to collectivelyherein as a single control system 320. The control system 320 maycontrol any number of variables and have any number of inputs, and mayuse an open-loop or closed-loop algorithm. Exemplary control systems 320include programmable logic control (PLC) devices having easily usedhuman machine interfaces, as are known in the art. Of course, thecontrol system 320 may simply comprise a human operator that monitorsthe various inputs and adjusts the various system variables.

The opened tow 312 preferably is pulled out of the forming jet assembly304 by a vacuum draw roll 322, such as the combining drum 800 describedelsewhere herein in conjunction with FIG. 8, or a similar drawingdevice. The opened tow 312 exits the forming jet assembly 304 at a towbreak angle Θ_(B), which may be adjusted by altering the position of thevacuum draw roll 322 (or similar device), or, more preferably, byadjusting the height and angle of the forming jet assembly 304 usingadjustable mounts 324. Increasing the tow break angle Θ_(B) increasesthe drag on the opened tow 312 and thereby increases the amount ofstretch that the vacuum draw roll 322 imparts on the opened tow 312.Greater stretch reduces the basis weight of the opened tow 312 that ispulled onto the vacuum draw roll 322. The tow forming jet 304 preferablyis aligned so that its outlet is tangential to the vacuum draw roll 322or slightly above a tangent to the vacuum draw roll 322. In a preferredembodiment, the outlet of the tow forming jet 304 is located at atangent to the vacuum draw roll 322 to about 1 inch above a tangent tothe vacuum draw roll 322. In a more preferred embodiment the outlet ofthe tow forming jet 304 is less than about 0.75 inches above a tangentto the vacuum draw roll 322, and in a most preferred embodiment, theoutlet of the tow forming jet 304 is located less than about 0.5 inchesabove a tangent to the vacuum draw roll 322. In another embodiment, theamount of stretch on the opened tow 312 may instead (or additionally) beregulated by operating the dancer 314 as a baffle (instead of using itas a level meter 314) to pinch down on the opened tow 312 as it ispulled onto the vacuum draw roll 322, and thereby increase the stretchof the opened tow 312. By using the dancer as a baffle, it is expectedthat adjustments of up to +/−10% may be made to the tow stretch or basisweight.

The tow forming jet's adjustable mounts 324 may be fixed in a desiredposition during machine operation, or may be actively operated by acontrol system 320 during operation in response to measurements of thecore basis weight or other feedback gathered during operation.Mechanical, electromechanical, pneumatic, hydraulic, or other suitableadjusting devices may be used to actuate the adjustable mounts 324, suchas stepper motors, solenoids and hydraulic or pneumatic pistons or rams,and the like. Alternatively, or in addition, the basis weight of theopened tow 312 may be adjusted by increasing or decreasing the speed ofthe vacuum draw roll 322, with faster speeds generally resulting in alower basis weight of the opened tow 312.

After the opened tow 312 exits the forming jet assembly 304, a supply ofsuperabsorbent particles 326 is delivered to the opened tow 312, and thetow/SAP composite is encased between first and second casing sheetsupplies 316, 318. Alternatively, the tow/SAP composite may be encasedwithin a fold in a single casing sheet. Preferably, as shown in FIG. 3,the opened tow 312 is laid onto a first casing sheet supply 316 beforethe SAP 326 is fed to the opened tow 312 to help contain the SAP 326 andcontrol the SAP distribution, then the second casing sheet supply 318 islaid on the tow/SAP composite to form an absorbent core subassembly thatmay be processed into absorbent garments.

The first and second casing sheet supplies 316, 318 encase the openedtow and SAP composite. The first and second casing sheet supplies 316,318 preferably form the first and second tissue layers 16, 18 of thecompleted garment, but may also form the topsheet 2 and backsheet 4 ofthe absorbent garment 10, or any other layers. The first and secondcasing sheet supplies 316, 318 are preferably wider than the opened tow312 that forms the absorbent core 6, and their side portions arepreferably sealed to one another by bonding or crimping to preventrelease of opened tow 312 and particles of SAP. The absorbent corecomposite 348, comprising the assembly of the first and second casingsheet supplies 316, 318 and the opened tow 312 and SAP 326 core, may befurther processed as it is conveyed through the assembly line forinclusion into absorbent garments 10. For example, in a preferredembodiment, the absorbent core composite 348 is severed into individualabsorbent cores 6, and the severed ends may be crimped or bonded toprevent the SAP 326 from exiting the ends.

In all cases, at least one of the first and second casing sheets 316,318 should be liquid permeable and positioned in the garment to face thewearer's body to allow the flow of fluids into the core 6. The othercasing sheet supply may optionally be liquid impermeable. The liquidimpermeability or permeability of either of the casing sheet supplies316, 318 may be provided by chemical or physical treatment, or by theproper selection of materials, as is known in the art. In an alternativepreferred embodiment, the first and second casing sheets 316, 318 mayboth be formed from a single sheet of material that is folded to encasethe opened tow 312 and SAP 326. In such an embodiment, the structure ofvarious parts of the system may be optionally be modified to facilitatethe manufacture of an absorbent core composite having a single casingsheet, as explained in more detail subsequently herein.

It may be desirable to apply an adhesive to one or both of the first andsecond casing sheet supplies 316, 318 prior to joining them with theopened tow 312 or tow/SAP combination. For example, in one preferredembodiment, an adhesive is applied to the entire width of one or both ofthe casing sheet supplies 316, 318 by adhesive applicators 328 beforethey are joined with the opened tow 312 to provide a better bond betweenthe casing sheets 316, 318 and the tow/SAP composite. In such anembodiment, the adhesive may also function to fix a portion of the SAPparticles 326 in place. In another preferred embodiment, the supplies ofcasing sheet material 316, 318 are wider than the tow/SAP composite, andadhesive is applied along the lateral edges of one or both of the casingsheet supplies to join them to one another, thereby sealing in thetow/SAP composite. Other uses of adhesives will be apparent to thoseskilled in the art based on the teachings provided herein.

A preferred adhesive for these and other embodiments is H2561U hot meltconstruction adhesive, available from Ato Findley, Inc. of Wauwatosa,Wis. Other suitable adhesives, known in the art, may be used providedthey do not excessively impair the desired properties of the casingsheet material (as described elsewhere herein), or add excessivestiffness to the absorbent core 6. For example, other adhesives mayinclude HL-1258 by H. B. Fuller Company of St. Paul, Minn.; Findley 2031and H2587-01 by Ato Findley Inc. of Wauwatosa, Wis.; and NS34-5665 byNational Starch Co. of Bridgewater, N.J. Other adhesives that may beused include 34-578A by National Starch Co. of Bridgewater, N.J. Inanother preferred embodiment, the adhesive may be selected to impartdesired properties to the casing sheet supplies 316, 318. For example,an adhesive may be used to render one of the casing sheet supplies 316,318 fluid impervious, opaque, hydrophobic (or hydrophilic), and so onthe adhesive may also be water soluble or have other beneficialproperties. Adhesive applicators that may be used with the presentinvention include spray applicators, such as those provided by NordsonCorporation of Westlake, Ohio, or other suitable applicators, as areknown in the art.

Still referring to FIG. 3, in a preferred embodiment the absorbent corecomposite 348 is assembled in four procedures that take place as thevarious parts of the assembly are pulled onto the rotating vacuum drawroll 322. In the first step, which takes place at location A, the firstcasing sheet supply 316 is drawn onto the vacuum draw roll 322. In thesecond step, at location B, the opened tow 312 is drawn onto the vacuumdraw roll 322 to overlay the first casing sheet supply 316 after beingpulled out of the forming jet assembly 304. In the third step, atlocation C, a supply of SAP 326 is deposited onto the opened tow 312 bythe vibratory feeder 332, as described herein. And in the fourth step,at location D, the second casing sheet supply 318 is brought in tooverlie the first casing sheet supply 316, opened tow 312 and depositedSAP. Those skilled in the art will appreciate that these steps may beperformed using equipment other than that specifically described herein,and may also be performed in various different orders, with some of thesteps being rearranged, omitted or combined, or with additional stepsbeing performed. Such variations are generally within the scope of thepresent invention.

Also in a preferred embodiment, a lay on roll 330 is used to press thesecond casing sheet supply 318 against the tow/SAP composite and thefirst casing sheet supply 316. The lay on roll 330 helps flatten thecore assembly and improves the edge seals between the first and secondcasing sheet supplies 316, 318. The lay on roll 330 may also be equippedto provide ultrasonic, heat, or other bonds between one or more of thefirst and second casing sheets 316,318 and the tow/SAP composite. Insuch an embodiment, the lay on roll 330 may cooperate with the vacuumdraw roll 322 or other device to create the desired bonds. For example,portions of the lay on roll 330 may form ultrasonic horns, whilecorresponding portions of the vacuum draw roll 332 form ultrasonicanvils that, together, form an ultrasonic bond between the first andsecond casing sheet supplies 316, 318.

The superabsorbent particles preferably are provided by a vibratoryfeeder 332, however any other suitable SAP feed device, such asauger-type feeders and SAP sprays also may be used. The vibratory feeder332 comprises a feed tray 334 that is attached to and driven by a motor340. The motor 340 vibrates the feed tray 334, moving it back and forthin the direction of vibration V, as indicated by the double-headed arrowin FIG. 3. The feed tray 334 is supplied from above by a hopper 336 byway of a flexible coupling 338 that helps isolate the hopper 336 fromthe movement of the feed tray 334. The vibratory feeder is preferablysuspended on one or more, and most preferably three, scales 342 thatweigh the vibratory feeder 332 and its contents. The vibratory feeder332 is preferably positioned so that none of its moving parts,particularly the motor 340 and feed tray 334 strike other parts of themachinery during operation.

The hopper 336 is preferably selected to provide consistent flowcharacteristics for a variety of superabsorbent polymers or otherparticulate and fibrous additives. In particular, it is preferred thatthe hopper 336 should flow all of its contents in a regular manner,described as “mass flow,” so that few or none of the particles becomestuck in the hopper 336, and do not experience sudden surges in the flowrate. Mass flow is present when essentially all of the material in thehopper is in motion whenever any material is withdrawn. This type offlow pattern is also described as first-in-first-out flow. In order toprovide the desired mass flow, the hopper 336 is preferably designed toavoid “bridging” (i.e., when particles become lodged in the hopper byforming a “bridge” or arch-like structure that resists flowing), and toavoid “ratholing” (i.e., when a column of particles flows through thecenter of the hopper 336, but those particles along the walls do notflow). When the hopper 336 provides mass flow, it is not necessary toprovide undesirable external forces, which may damage or redistributethe particles, to shake unmoving particles free. Mass flow may beobtained by providing the hopper 336 with relatively smooth interiorwalls and by avoiding the use of shallow flow angles within the hopper336. The design may vary depending on the particulate matter or SAP 326being held in the hopper 336, and it may be desirable to test theproperties of the material, such as the material's slip angle and angleof repose, to obtain a suitable hopper design. The design of mass flowhoppers is generally known in the art, and a skilled artisan will beable to design a suitable hopper without undue experimentation based onthe teachings provided herein.

In one embodiment, the hopper has a capacity of about 1.5 ft³ to about10 ft³, and more preferably about 2.25 ft³ to about 6 ft³, and mostpreferably about 3 ft³. Also in a preferred embodiment, the hopper 336discharges through an outlet having a diameter of about 4 inches toabout 12 inches, and more preferably about 5 to about 9 inches, and mostpreferably about 7 inches. The hopper 336 may be supplied and refilledwith SAP using any device and method known in the art. In a preferredembodiment, the hopper 336 is filled by a screw (or “auger”) typeconveyor that moves SAP from a supply source into the hopper 336. Thedesign of such hoppers 336, conveyors and supply sources is known in theart, and a skilled artisan will be able to provide a hopper 336 for usewith the present invention without undue experimentation based on theteachings provided herein.

In a preferred embodiment, the hopper 336 is derived from a SOLIDSFLOWMODEL 5007 DRY MATERIAL FEEDER. Also in a preferred embodiment, thehopper 336 is supplied and refilled from a SOLIDSFLOW MODEL SBS BULK BAGDISCHARGE STATION using a FLEXICON flexible screw (auger) conveyor,which is controlled by a SOLIDSFLOW MODEL 1200 LOSS-IN-WEIGHTCONTROLLER. All of these devices are available from SolidsFlowCorporation of Fort Mill, S.C.

The vibratory feeder 332 may be suspended from one or more, and mostpreferably three, scales 342 that measure the weight of the vibratoryfeeder 332 and its contents. The scales may be used to calculate theamount of SAP 326 that is being distributed onto the opened tow 312.Such systems are commonly known as “loss-in-weight” systems, as theycontinuously measure the reduction in weight of the vibratory feeder 332as its contents are being emptied. The conveyors and supply sources thatfeed into the hopper 336 may also be suspended on scales so that SAP maybe added to the hopper during operation, while still being able tocalculate the amount of SAP being deposited onto the opened tow 312. Ina preferred embodiment, the loss-in-weight measurements of the scales342 are used with a closed-loop feedback circuit to control the amountof SAP 326 that is deposited onto the opened tow 312. Such a circuit ispreferably integrated into a control system 320 that may control otherfeatures and operation of the vibratory feeder 332 and related devices.The scales 342 may also be used to determine when it is necessary ordesirable to refill the hopper.

The scales 342 are preferably able to read to an accuracy that allowsuseful determination of the amount of SAP being deposited onto theopened tow 312. In a preferred embodiment, the scales 342 read to anaccuracy of about +/−10 grams, and more preferably of about +/−1 gram,and most preferably of about +/−0.1 gram. In a preferred embodiment, thescales 342 comprise strain gauge-type load measurement cells, such asthose available under the designation SOLIDSFLOW MODEL 1000 SCALEASSEMBLY from SolidsFlow Corporation of Fort Mill, S.C. The design,construction, and use of scales suitable for use with the presentinvention is known in the art.

A flexible coupling 338 preferably joins the hopper 336 to the feed tray334. The flexible coupling 338 is used pass SAP or other additives fromthe hopper 336 to the feed tray 334, while simultaneously isolating thehopper 336 from the vibratory movement of the feed tray 334 and motor340. The flexible coupling 338 may comprise any durable flexiblematerial, such as canvas and other cloths, or natural or syntheticrubbers. It is preferred that the flexible coupling does not damp orimpede the desired vibrating motion of the feed tray 334 and motor 340,and thereby impair the ideal SAP feeding. For example, if the flexiblecoupling 338 is too rigid, it will reduce the ability of the motor 340to vibrate the feed tray 334 because it will resist deformation,effectively increasing the mass of the feed tray 334. Also, if theflexible coupling 338 is too elastically resilient, it will tend tostore energy created in it when the feed tray 334 and motor 340 arevibrating, and return this stored energy in an uncontrolled manner(i.e., vibrate on its own) thereby creating additional uncontrolledvibrations in the feed tray 334 and motor 340. It also is preferred thatthe flexible coupling 338 be as light as possible so as to reduce theinertia that must be overcome by the motor 340 during operation. In apreferred embodiment, the flexible coupling 338 comprises a rubbermaterial having a diameter and shape selected to join the outlet of thehopper 336 with the inlet chute 402 of the feed tray 334.

The feed tray 334 and motor 340 preferably are suspended below thehopper 336 by flexible mounts 344 that allow the motor 340 and feed tray334 to move relative to the hopper 336. The flexible mounts 344 maycomprise rods having flexible or pivoting couplings joining them, ateach end, to the hopper 336, motor 340 and feed tray 334. In a preferredembodiment, the flexible mounts 344 are designed to convey a minimalamount of vertical movement or vibration to the hopper 336, which maycause the scales 342 to read inaccurately. In such a preferredembodiment, the flexible mounts 344 may be joined to one or more of thehopper 336, motor 340 and feed tray 334 by a dry or liquid-filledelastomeric bushing or coupling. The design and selection of suchvibration- and movement-damping couplings are known in the art, and askilled artisan will be able to select or produce an appropriatecoupling system based on the teachings provided herein.

Referring now to FIG. 4, the feed tray 434 preferably comprises an inletchute 402 that is attached to the flexible coupling 338 to receive SAP326 from the hopper 336. A pan 404 extends away from the inlet chute 402at a downward angle a to an outlet edge 406 of the feed tray 334. Thepan 404 may also comprise multiple sections that descend at varyingangles. The feed tray 334 preferably is covered along most of its lengthto prevent disturbances of the SAP 326 or other particulate additives.The covered portion preferably terminates at an adjustable gate 408located near the outlet edge 406 of the feed tray 334. The adjustablegate 408 is spaced above the pan 404 and generally divides the feed trayinto an upstream portion from which the SAP 326 flows and a downstreamportion. The adjustable gate 408 may be operated manually, or may beopened and closed by an actuating device, such as an electromechanical,mechanical, pneumatic, or hydraulic device. Such an actuating device mayoptionally be controlled by a control system 320 using a closed-loopfeedback algorithm or open-loop algorithm. Such actuating devices areknown in the art, and a skilled artisan will be able to employ asuitable actuating device without undue experimentation. Of course, inone embodiment the gate may be a fixed gate, rather than an adjustablegate.

In a preferred embodiment, the SAP 326 or other particulate additivematerial exits the feed tray 334 at its outlet edge 406 in acurtain-like stream having a consistent flow rate across its entirewidth. Referring to FIG. 7, the active width W_(A) of the feed tray 334is the width of the portion of the feed tray 334 from which the SAP 326flows (which may be affected by the use of SAP guides 410, as describedelsewhere herein), and generally corresponds to the width of the SAPflow. The active width W_(A) may vary from one application to the next,and may be varied during operation by using, for example actuatedpivoting SAP guides 410 that move together and apart under the controlof a control system 320. Generally, the active width W_(A) preferably isapproximately the same width as the opened tow 312. In one embodimentthe active width W_(A) is about 2 inches to about 12 inches, and is morepreferably about 3 inches to about 10 inches, and, in a particularlypreferred embodiment, the active width W_(A) is as about 3.75 inches toabout 4 inches.

In other embodiments it may be desirable to vary the flow rate of theSAP 326 in particular areas to provide zoned absorbency. Referring nowto FIG. 15 the pan 404 may be contoured or shaped to provideconcentrated flows of SAP during operation or to otherwise control theflow of the SAP. For example, in one embodiment the pan 404 may have oneor more depressions 1502 along the outlet edge 406 that effectivelyincrease the downward angle a at the depressions 1502. In such anembodiment, the SAP 326 may tend to funnel into the depressions 1502,and those portions of the opened tow 312 that pass beneath thedepressions 1502 should receive a relatively high concentration of SAP326. In another embodiment, the pan 404 may have troughs 1504 thatextend below the adjustable gate 408, effectively increasing the heighth of the adjustable gate 408 at those points to increase the flow rateof SAP through the troughs 1504. Such troughs 1504 may extend to theoutlet edge 406 to additionally act as depressions 1502, as describedabove. Other variations in the outlet edge 406 and pan 404 geometry willbe apparent to those skilled in the art based on the teachings providedherein.

In one embodiment, the feed tray 434 may have more than one inlet chute402 so that a number of different supplies of SAP may be fed into it.The supplies of SAP may comprise different types of SAP that are blendedor isolated from one another using internal baffles and guides. In suchan embodiment, for example, one type of SAP may be distributed to thelateral sides of the opened tow 312, and another type of SAP may bedistributed to the central region of the opened tow 312. Othervariations and uses of a feed tray 334 having multiple inlet chutes 402will be apparent to those skilled in the art based on the teachingsprovided herein.

SAP guides 410, comprising vertical or angled strips of material,optionally may be integrated into the feed tray 334 on either side ofthe adjustable gate 408 to serve a number of purposes. The SAP guidesare preferably attached to the pan 404, but may also be attachedelsewhere to the feed tray 334 or to other objects. In a preferredembodiment, the guides contain the lateral movement of the SAP 326 sothat it falls only in a center region of the opened tow 312. In anotherpreferred embodiment, the SAP guides 410 isolate the flow of SAP 326from turbulent airflow around the feed tray 334 to provide more even SAPdistribution. The SAP guides 410 may be proximal to the outlet edge 406,as shown in FIG. 4, or may be located elsewhere on the pan 404. The SAPguides 410 may also be used to isolate or blend different supplies ofSAP. In one embodiment, the SAP guides 410 may also comprise additionalvertically stacked layers, in addition to the pan 404, that may containseparate flows of SAP. In a preferred embodiment, the SAP guides 410 arespaced apart by about 3.75 inches to about 4 inches to provide about a3.75 inch to about 4 inch wide flow of SAP.

Referring now to FIGS. 5A and 5B, the feed tray 334 operates on theprinciple that particulate solids within them, such as SAP 326, willrest at their angle of repose until disturbed by vibrations induced bythe motor 340. This principle of operation is more fully disclosed inU.S. Pat. No. 3,973,703 to Peschl, which is incorporated by referenceherein in its entirety and in a manner consistent with the presentinvention (hereafter referred to herein as “Peschl”). It should beunderstood that, although the inventors provide various theories on themodes of operation of the vibratory feeder 332, the invention is notintended to be limited to these or other modes or theories of operation.

It has been found that the flow of the SAP 326 generally may beinfluenced by the properties of the SAP, the downward angle a of the pan404, the rate of vibration of the motor 340, the trailing distance d ofthe pan 404, and the height of the adjustable gate 408. In theembodiment shown in FIG. 5A, the feed tray 334 is shown at rest, withthe SAP 326 being contained within the feed tray 334. In the embodimentof FIG. 5A, the downward angle a is greater than the angle of repose ofthe SAP 326, and so any SAP remaining along the trailing distance d ofthe pan 404 slides off the pan 404 after the motor 340 stops vibrating.The remaining SAP 326 is caught behind a bridge 502 of SAP that forms byfriction between the particles of SAP, cohesion between the SAPparticles, or both. The adjustable gate height h may be adjusted toprovide ideal SAP containment and control. Raising the adjustable gate408 generally provides a greater SAP flow rate for a given motorvibration frequency, while lowering the adjustable gate 408 generallyprovides the opposite result. The adjustable gate height h preferably isadjusted to ensure that a bridge 502 forms promptly after the motor 340stops vibrating the feed tray 334 to stop the flow of SAP 326 as quicklyas possible.

The flow rate of the SAP generally follows the vibration rate of themotor 340, and stops flowing almost immediately upon shut down of themotor 340. Generally, faster motor vibration rates provide greater SAPflow rates and slower motor vibration rates provide a slower SAP flowrate. There is little or no appreciable time delay between changes inthe motor frequency and the flow rate of the SAP 326, so the vibratoryfeeder 332 provides relatively accurate control of the SAP flow,especially when compared to known methods of distributing SAP ontoopened tow 312 or fluff pulp.

It should be noted that SAP remaining on the trailing distance d of thepan 404 may continue to flow at an uncontrolled rate after the motorfrequency changes, but such lag time has not been found to cause anappreciable detriment to the device's ability to accurately deposit SAP326 onto the opened tow 312. If a detriment is found, however, thetrailing distance d may be reduced to make the SAP flow rate follow themotor frequency variations more closely. Reducing the trailing distancemay also increase the flow rate of the SAP for a given motor frequencyand adjustable gate height h, as is explained in more detail in Peschl.In one embodiment, the trailing distance may be reduced to zero, and theoutlet edge 406 even may be within the upstream portion of the feed tray334 (i.e., the adjustable gate 408 may be located beyond the outlet edge406).

In a more preferred embodiment, shown in FIG. 5B, the downward angle amay be less than the SAP's angle of repose and slip angle (i.e., theangle at which the SAP 326 will slide down the surface of the pan 404),so that when the feed tray 334 is at rest the SAP remaining along thetrailing distance d stays on the pan 404. In such an embodiment, theaforementioned lag between SAP flow and motor frequency changesassociated with the SAP located in the trailing distance d may bereduced.

Referring back to FIG. 4, it has been found that the feed tray's outletedge 406 should be located as close as possible to the vacuum draw roll322. Reducing the offset distance c between the outlet edge 406 and thevacuum draw roll 322 provides a number of benefits. In particular,minimizing the offset distance c allows the SAP to fall onto the openedtow 312 as quickly as possible, minimizing any redistribution ordiffusion of SAP 326 that may be caused during a longer fall byturbulent air flowing around the feed tray 334 and by interactionbetween the SAP particles 326. Reducing the offset distance c alsodecreases the lag time between changes in motor speed 340 and changes inthe amount of SAP 326 being distributed to the opened tow 312. In apreferred embodiment, the offset distance is about 0.25 inches to about4.00 inches, and more preferably about 0.375 inches to about 1.00 inch,and most preferably about 0.50 inches.

The minimum value for the offset distance c may be affected by machineoperating tolerances, such as to prevent contact between the open tow312 or the vacuum draw roll 322 and the vibrating feed tray 334, or byother factors, such as the tolerances of the casing sheet supplies 316,318 and opened tow 312. For example, in a preferred embodiment, theoffset distance c is at least about 0.50 inches to allow passage ofclumped aggregations of opened tow 312, that may be present duringstartup and during other operating conditions.

In a preferred embodiment that may be used with a variety of SAPs, thedownward angle α, as measured relative to horizontal, is about 10degrees to about 45 degrees, and more preferably about 12 degrees toabout 30 degrees, and most preferably about 15 degrees. Also in apreferred embodiment, the adjustable gate height h is about 0.10 inchesto about 1.00 inches, and more preferably about 0.125 inches to about0.75 inches, and most preferably about 0.25 inches to about 0.50 inches.Also in a preferred embodiment, the trailing distance d is about 0.25inches to about 8 inches, and more preferably about 2 to about 6 inches,and most preferably about 4 inches. Also in a preferred embodiment, theinlet chute 402 has a diameter of about 4 inches to about 12 inches, andmore preferably about 5 to about 9 inches, and most preferably about 7inches. In a preferred embodiment, the feed tray 334 may be derived froma SOLIDSFLOW MODEL 5000 DRY MATERIAL FEEDER, available from SolidsFlowCorporation of Fort Mill, S.C.

Referring now to FIGS. 6 and 7, the feed tray 334 preferably is equippedwith side plates 602 that help isolate the SAP 326 and opened tow 312from lateral airflow and may help contain the lateral movement of SAP326 after it exits the feed tray 334. Such lateral airflow and otherairflow may disturb the desired distribution of SAP onto the opened tow312. The side plates 602 are preferably oriented approximately parallelto the machine direction of the opened tow 312 (i.e., within about 20degrees of parallel) and sized to substantially reduce or block air fromflowing laterally into the area beneath the feed tray 334. Preferably, afirst edge 604 of each side plate 602 is located proximal to the vacuumdraw roll 322 (or other similar drawing device); and a second edge 606of each side plate 602 is located proximal to the forming jet assembly304. The side plates 602 are preferably shaped and sized so that they donot strike any other parts of the machine as they are vibrated back andforth. A third edge 608 of each side plate 602 preferably is adapted toconform to the second casing sheet supply 318 to help prevent lateralairflow from above the feed tray from encroaching upon the supply of SAP326. In such an embodiment, it also may be desirable for the top edge610 of the adjustable gate 408 to be proximal to the second casing sheetsupply 318 to further reduce the amount of air that flows in topotentially disturb the SAP 326. The SAP guides 410 may also have anedge 612 contoured to be adjacent to the second casing sheet supply 318to further inhibit the development of undesirable airflow near the SAP326. The side plates 602 preferably may be adjusted in at least thevertical direction, as indicated by the double-headed arrow in FIG. 6.In other embodiments, the side plate 602 may be attached to somethingother than the feed tray 334, but in such embodiments, care should betaken to prevent the moving feed tray 334 from striking the side plates602 during operation.

Referring back to FIG. 4, the motor 340 is used to initiate and modulatethe flow of SAP 326 out of the feed tray 334. The motor 340 vibrates thefeed tray 334 by moving it back and forth in the direction of vibrationV, as indicated by the double-headed arrow in FIG. 4. In a preferredembodiment, both the pitch p and frequency of the motor 340 may beadjusted to modulate the flow of SAP 326. It has been found thatincreasing the motor's pitch p (i.e., the distance traversed by themotor during each cycle) generally increases the SAP flow rate, andvice-versa. Also, as noted before, it has been found that increasing themotor's frequency generally also increases the SAP flow rate, andvice-versa.

The effectiveness of the motor 340 and amount of control provided by themotor 340 are affected by the weight and rigidity of the feed tray 334.If the feed tray 334 is too heavy, its inertia will resist the forcesimparted upon it by the motor 340, and the motor 340 may not be able toaccelerate and decelerate it back and forth to create the desired pitchp distance or frequency vibrations. If the feed tray 334 is not rigidenough, it will flex as the motor 340 imparts forces on it. As the feedtray 334 flexes, it absorbs the energy that was intended to move thefeed tray 334 and does not accurately follow the path intended by themotor 340. The energy absorbed by a flexible feed tray 334 may bereleased in the form of undesirable variations in the intended pitch pand frequency of vibration. It has been found that it is generallydesirable to make the feed tray 334 as light and as rigid as possible inorder to provide the greatest amount of control of the SAP flow.

In a preferred embodiment, the motor 340 is coupled to the feed tray 334through a coupling 412. In order to provide accurate transmission of themotor's vibrations to the feed tray 334, the coupling 412 should berigid in the vibration direction V, and the coupling 412 preferably hasa box-like shape or C-shape. Also in a preferred embodiment, the inletchute 402, which may comprise a relatively large open space that may besusceptible to undesirable flexing, is reinforced with a structuralmember, such as a tubular brace 414 aligned in the vibration directionV. In an embodiment in which the inlet chute has a diameter of about 7inches it has been found that a tubular brace 414 of about 1 inchdiameter is suitable to reduce undesirable flexure in the inlet chute402 without adversely affecting the flow of SAP through the inlet chute.In other embodiments, in which the inlet chute 402 contains baffles orother internal flow-directing or flow-controlling structures, thesestructures may also serve to increase the feed tray's rigidity, makingit unnecessary to reinforce the inlet chute 402.

As noted before, the motor 340 and feed tray 334 are suspended beneaththe hopper 336 by flexible mounts 344 that allow both the motor 340 andthe feed tray 334 to move independently of the hopper 336. As such, asthe motor 340 vibrates the feed tray 334 back and forth, the motor 340itself may also move back and forth. In a preferred embodiment, the massof the motor 340 is significantly greater than the combined mass of thefeed tray 334 and the SAP 326 contained therein, and so the movement ofthe motor 340 will be insignificant relative to the movement of the feedtray 334. In such an embodiment, the motor's pitch p will be almostentirely converted into movement of the feed tray 334 (as is shown inFIG. 4). If, however, the motor 340 does experience a significant amountof movement, more of the pitch p will be converted into the motor'smovement, and less of the pitch will result in movement of the feed tray334. This reduction in the movement of the feed tray 334 may result inless effective SAP distribution and control. If it is found that themovement of the motor negatively affects the SAP distribution andcontrol, the motor's movement may be restricted, or the pitch p may beincreased to increase the effective movement of the feed tray 334. Othermeasures may also be taken to counteract such negative affects. Thoseskilled in the art will be able to measure or calculate the movement ofthe motor 340 and feed tray 334 and make accommodations in the design ofthe apparatus for such movements using the teachings provided herein.

In a preferred embodiment, the motor 340 comprises an electromagneticvibrator, such as those supplied by Eriez, Corporation of Erie, Pa. asModel Number 30A, part number 3N-56743. Such a motor may be selected tobe driven by any available power source, such as a 115 volt, 60 Hz powersource. The motor may also require specific support or drive hardwareand software, such as an Eriez VTF signal following controller boardthat is supported by and AB SLC 0-20 mA analog card, available fromAllen-Bradley Company of Milwaukee, Wis. Other motors 340 may also beused, such a rotary motor that is configured to provide cyclical lateralmovement or vibrations to the feed tray 334. Other useful motors 340include pneumatic, magnetic, electric and hydraulic actuators, and thelike, as long as they can provide the necessary forces to vibrate thefeed tray 334 at the desired pitch p and frequency. Electromagneticvibrators are preferred, as they typically provide relativelycontrollable movement and consume less energy than other devices.

In one embodiment that should be suitable for dispensing a variety ofSAP materials, the motor 340 may be operated from a standstill (zero Hz)up to about 430 Hz, and more preferably up to about 520 Hz, and mostpreferably up to about 600 Hz. In a preferred embodiment that should besuitable for dispensing a variety of SAP materials, the frequency isapproximately constant, and the flow rate of the particulate matter iscontrolled by modulating the motor's pitch. In such a preferredembodiment, the motor frequency is about 60 Hz, and the pitch p of themotor variable between about 0.01 inches to about 0.125 inches, and morepreferably about 0.02 inches to about 0.10 inches, and most preferablyabout 0.04 inches to about 0.08 inches. Such adjustments may beobtained, for example, by varying the voltage of the motor between about0 and about 90 volts.

Such a vibratory feeder 332 may be adapted to provide a high volume ofSAP flow, and may be used at relatively high manufacturing line speeds.It is anticipated that a vibratory feeder produced according to apreferred embodiment of the present invention may be used with anassembly line producing diapers at a rate in excess of 600 products perminute. The vibratory feeder 332 preferably can feed superabsorbentpolymer or other additives at a rate of about 10,000 grams per minute(g/min) to about 20,000 g/min, and more preferably at a rate of about12,500 g/min to about 17,500 g/min, and most preferably at a rate ofabout 15,000 g/min. In a preferred embodiment, the hopper 336 is fed bya screw-type conveyor or other conveyor that has a capacity to maintaina useful level of SAP 326 in the vibratory feeder 332. The conveyor mayhave a feed rate that is less than the maximum feed rate of thevibratory feeder 332, so long as the average feed rate of the vibratoryfeeder 332 does not exceed the average feed rate of the conveyor.

Superabsorbent polymers and other particulate additives can berelatively expensive, and so it is often desirable to minimize theamount of SAP that is placed in the core and to “zone” such additivesonly where they are most beneficial for the final product. Such zoningis also particularly beneficial in tow-based absorbent cores because thelack of fluff pulp in such cores may reduce the overall wickingcapability of the core, making it more important to place the SAP closerto the location where fluid is likely to strike the garment. In apreferred embodiment, the motor 340 is controlled by a control system320 to provide a desirable distribution of SAP 326 into the opened tow312. In one preferred embodiment, such a control system 320 may be usedto operate the motor 320 to deposit a steady stream of SAP 326 onto theopened tow 312 to provide a uniform opened tow/SAP mixture in theabsorbent cores that are ultimately formed by the process. In anotherpreferred embodiment, the control system may cyclically increase anddecrease the pitch p and/or frequency of the motor 340 to deposit apulsating supply of SAP 326 to the opened tow 312, thereby providing theabsorbent cores with targeted concentrations of SAP that provide thegarment 10 with zoned absorbency. Preferably, the control system 320uses a closed-loop feedback method that considers various factors indetermining how much SAP to distribute at any given moment.

In a preferred embodiment, the control system 320 is provided withinformation about how fast the assembly line is running by using, forexample, a tachometer 346 on the vacuum draw roll 322 or by any othersuitable line speed measuring device (See FIG. 3). By integrating such aline speed measuring device into the control system 320, the controlsystem 320 may be programmed to increase or decrease the pitch p orfrequency of the motor 340 to vary the SAP flow rate as the productmanufacturing rate changes, thereby providing all of the products withthe proper amount of SAP, regardless of the assembly line speed. Such acapability provides a lower rate of product rejection duringtransitional phases, thereby improving the overall efficiency of themanufacturing process.

In another preferred embodiment, the output of the scales 342 isintegrated into the control system 320. By considering the weight of theSAP being distributed, as measured by the scales 342, the control system320 may programmed to modulate the motor 340 to accurately distributeSAP at the desired flow rate. In such an embodiment, the control system320 may also accommodate for deviations in the flow characteristics ofthe SAP particles to continue to provide an even flow, such as byincreasing the vibration rate if it is found that the SAP is not flowingas rapidly as expected, and vice-versa. Such deviations may be caused bytypical variations in the shape, size, humidity, density, or otherfeatures of the SAP, or may be caused when a different SAP product isused in a machine that was originally set up for another type of SAP orset up for a SAP provided by a different supplier.

A closed-loop feedback control system 320 may also be programmed to stopdistributing SAP in the event that a fault is detected in the processingline. For example, if a fault detection circuit tied into the controlsystem 320 determines that one or more products will be defective uponcompletion, the flow of SAP may be stopped so that the defectiveproducts will not receive SAP. In such an embodiment, it may bedesirable to produce the absorbent cores of the garments as late aspossible in the manufacturing process in order to detect as many defectsas possible before preparing the absorbent core 6 for each product.

In one embodiment, a SAP concentration detection device 350 (FIG. 3) maybe integrated into the control system 320 to provide further detectionand control capabilities to the control system 320. The concentrationdetection device 350 may be located to measure the amount and/orlocation of SAP in the assembled absorbent core composite 348. If theamount of location of the SAP is not present as desired, theconcentration detection device 350 may signal this to the control system320 so that appropriate corrections in the SAP feed rate may be made.Those skilled in the art are capable of designing or utilizing asuitable SAP concentration detection device 350 using the guidelinesprovided herein.

The flow rate of the SAP may also be controlled by a control device 320by actively adjusting the height h of the adjustable gate 408 duringoperation. As noted before, the adjustable gate 408 may be raised andlowered during operation to increase and decrease, respectively, theflow rate of the SAP 326. Such adjustments may also be made to provide acyclically fluctuating amount of SAP to the opened tow 312 to createtargeted regions of relatively high SAP concentration for zonedabsorbency. In such an embodiment, the control device 320 may operatethe adjustable gate 408 in conjunction with the scales 342, tachometer346, concentration detection device 350, or other sensors to provideclosed-loop feedback control of the SAP flow. A suitable actuationdevice for cyclically raising and lowering the adjustable gate 408preferably does not cause excessive vibrations or other movements thatmay cause the scales 342 to read inaccurately.

Referring now to FIG. 8, it has been found that a “combining drum”-typevacuum draw roll 800 may be advantageously used in conjunction withvibratory feeders 332, such as those described herein, or,alternatively, with other SAP feed devices and methods, such as thosethat are known in the art. The combining drum 800 is characterized inthat several or all of the parts that eventually form the absorbent core6 of the garment 10 are assembled in a continuous motion around all orpart of the combining drum's circumference. In a preferred embodiment,the combining drum 800 combines the first casing sheet supply 316,opened tow 312, SAP 326 and second casing sheet supply 318 (i.e.,various constituent parts of the core composite 348, which may, ofcourse, include other parts) in a substantially continuous operation asthey are conveyed by the combining drum 800. Each of the parts may beconveyed to the combining drum 800 separately and then joined togetherinto an integrated structure, or alternatively, some of the parts may bejoined to one another prior to contact with the combining drum 800. Forexample, an additional layer 20 may be affixed to either side of one orboth of the first and second casing sheet supplies 316, 318 before thesupply is provided to the combining drum 800.

As noted before, a preferred combining process has been generallydescribed elsewhere herein with reference to Locations A, B, C and D ofFIG. 3. The operation of the combining drum 800 described herein isrelatively simple compared to many known core-forming apparatus, and maybe adapted to operate at high line speeds. For example, it isanticipated that the combining drum 800 may be adapted to operate withan assembly line producing in excess of 600 diapers per minute.

In a preferred embodiment the combining drum 800 has a generallycylindrical surface 802 with a vacuum surface 804 forming acircumferential belt on the cylindrical surface 802. The vacuum surface804 comprises one or more holes 806 through which a vacuum is applied tothe various parts of the core composite 348. The holes 806 in the vacuumsurface 804 may be formed by any means known in the art, such asdrilling, machining, casting and so on. In a preferred embodiment, theholes 806 have a diameter of about 0.0625 inches to about 0.75 inches,and more preferably of about 0.125 inches to about 0.625 inches, andmost preferably of about 0.25 inches to about 0.50 inches. Also in apreferred embodiment, the holes may be spaced from one another by acenter-to-center distance of about 0.10 inches to about 1.00 inch. Theholes may be spaced in a rectilinear array, as staggered rows, or in anyother pattern that conveys the desired amount of vacuum. The vacuumsurface 804 also may comprise any other relatively rigid foraminousstructure, such as one or more mesh screens or removable perforatedplates that are affixed to openings in the cylindrical surface 802. In apreferred embodiment, the combining drum 800 may also comprise landingareas 808 on either side of the vacuum surface 804 which may be treatedto enhance their ability to grip the first and second casing layersupplies 316, 318. A vacuum is applied to the combining drum 800 througha vacuum port 810.

Referring now to FIG. 9, there is shown a sectional view of the vacuumsurface 804 region of a combining drum 800 as is appears just aftercombining the first casing sheet supply 316, opened tow 312, SAP 326 andsecond casing sheet supply 318 into an integrated core composite 348.The width W₁ of the vacuum surface 804 (as measured in a directionparallel to the rotational axis of the combining drum 800) preferablycorresponds approximately to the width of the opened tow 312 and to thewidth of the portion of the feed tray 334 from which SAP 326 isprovided. The first and second casing sheet supplies 316, 318 arepreferably wider than the opened tow 312, and their excess width islocated in side areas 902 that overlie the landing areas 808. The firstand second casing sheet supplies 316, 318 preferably are joined to oneanother in their side areas 902 by adhesive bonding, other methodsdescribed elsewhere herein or by other methods known in the art. Asnoted elsewhere, a lay on roll 330 may be used to help join the firstand second casing sheet supplies 316, 318 by use of pressure, crimpingnodules, and the like.

In a preferred embodiment, the vacuum surface 804 is recessed in thecylindrical surface by a depth y of less than about 0.50 inches, andmore preferably by less than about 0.10 inches, and most preferably byabout 0.030 inches. It has been found that having a slight increase inthe diameter of the combining drum 800 on either side of the vacuumsurface 804 (i.e., a recessed vacuum surface 804) helps keep the firstcasing sheet supply 316 stretched across the combining drum 800 duringoperation.

The vacuum surface width W₁ may be selected to provide certain benefitsto the garment into which the core composite 348 is being integrated. Inone embodiment, the core composite may be integrated into the garment ina flat state, in which case it may be desirable to make the vacuumsurface width W₁ and the width of the opened tow 312 equal to thedesired width of the garment's absorbent core 6. However, the corecomposite 348 may be stretched, folded, or otherwise resized duringmanufacture, in which case the vacuum surface width W₁ should becorrespondingly adjusted. In a preferred embodiment, the core composite348 is folded at least once before being integrated into the garment.Folded absorbent cores have been discussed in more detail elsewhereherein. In a preferred embodiment, the vacuum surface width W₁ is about1.75 inches to about 12 inches, and more preferably about 2.75 inches toabout 10 inches, and most preferably about 3.75 inches. In order toreduce SAP loss during core formation, the vacuum surface width ispreferably slightly narrower (about 0.10 inches on either side) than thewidth of the supply of opened tow 312 to promote a slight inwardmigration of SAP away from the side areas 902.

As noted before, it has been a continuing challenge to provide thedesired distribution of SAP within the absorbent cores 6 of absorbentgarments 10. It has been found that a combining drum 800 as describedherein may be beneficially used to help provide such desired SAPdistributions. Cellulose acetate opened tow 312 and other types of lowdensity fibrous opened tow structures allow a relatively large amount ofair to pass through them compared to conventional fluff pulp materials,and the location of the SAP 326 may be effectively controlled bymodulating the amount and position of the vacuum applied to theSAP/opened tow mixture. It has been found that the distribution of theSAP can be more easily controlled with tow/SAP cores than with fluff/SAPcores. As air passes through the opened tow 312 into the vacuum itconveys the SAP 326 through the fibrous structure, and the SAP particles326 generally tend to concentrate more densely at areas having a highvacuum. Also, as the vacuum is increased, the SAP particles 326generally move closer to the surface of the opened tow 312 that isadjacent the combining drum 800. The degree to which the SAP migratestowards the high vacuum areas may also be affected by the duration oftime that the vacuum is applied to the SAP 326. The vacuum also helpsprevent SAP 326 from escaping out of the opened tow 312 duringmanufacturing. It has been found that a desirable mixture of SAP 326within the opened tow 312 and reduced SAP loss may be produced using avacuum of about 2.50 inches of water to about 20 inches of water, andmore preferably of about 3.75 inches of water to about 12.5 inches ofwater, and most preferably of about 5.0 inches of water. The vacuum maybe pre-set or may be manually or actively controlled by a control system320 using an open-or closed-loop feedback system.

In addition to being useful for providing a homogeneous dispersion ofSAP 326 in the opened tow 312, a combing drum 800 as described hereinmay also be used to accomplish various other desirable SAP distributionpatterns. In one embodiment, the vacuum level may be modulated toprovide a desirable depth of SAP penetration throughout the opened tow312 or only in discrete areas of the opened tow 312. In otherembodiments, the combining drum 800 may be adapted to provide machinedirection (MD) and cross-machine direction (CD) zoning of the SAPparticles 326 that provide the garment 10 with zoned absorbency. Themachine direction is the direction in which a part or assembly movesduring processing, and the cross-machine direction is perpendicular tothe MD. The machine direction generally corresponds to the longitudinaldimension 100 of the fully-assembled garment 10 (see FIG. 1), and thecross machine direction corresponds to the lateral dimension 102 of thegarment, however other relationships may also be used and are within thescope of the present invention.

Referring now to FIG. 10, regions of high SAP concentration, and thusgreater absorbency, may be provided in the MD and CD by making thevacuum surface 804 with particularly designed target regions 1002 thatconvey a greater amount of vacuum to portions of the opened tow 312.Such target regions 1002 may have larger holes and/or a greaterconcentration of holes in those areas where a greater concentration ofSAP 326 is desired. The larger amount of open space provided in suchregions will allow a greater amount of airflow into the vacuum, and thuscause a greater amount of SAP to migrate to those areas. For example, inthe embodiment of FIG. 10, the region 1004 has a greater concentrationof larger holes, which should provide a SAP concentration in the portionof the core composite 384 adjacent region 1004. The particular patternof SAP concentration may be adjusted by making each of the targetregions 1002 from a removable plate 1006 having the desired holepattern. Substitute plates 1006 may be easily machined to providedifferent hole patterns and zoned absorbency patterns.

In another embodiment, shown in FIG. 11, the vacuum surface 804 may beseparated into discrete target regions 1102, which may have varyingwidths, to provide zones of high and low MD and CD SAP concentrations.

In an embodiment in which the combining drum 800 has target regions1002, 1102 for providing zoned absorbency, the combining drum diameterD₁ should be selected so that the corresponding parts of each targetregions 1002, 1102 are spaced from one another around the circumferenceof the combining drum 800 by a distance corresponding to the absorbentcore length X₁. By using such a spacing, each target region 1002, 1102will create a targeted zone of SAP that will be properly located in eachabsorbent core 6 that is cut from the core composite 348.

It should be understood that by providing a distance betweencorresponding parts of each target region 1002, 1102 that isapproximately equal to a core length X₁, the circumference of thecombining drum 800 will be sized to equal a whole number multiple of thecore length X₁. At a minimum, the circumference can equal one corelength X₁, but in such an embodiment, the various parts of the corecomposite 348 will be in contact with the vacuum for relatively littletime, which may lead to inadequate SAP distribution or other formingproblems. Smaller diameter drums may also be subject to greatervibration. These problems may become exacerbated when the vacuum drum800 is used with higher speed assembly lines. Problems may also be existwith larger drum diameters. For example, the manufacturing tolerancesfor a larger diameter drum may be less precise. In addition, as the sizeof the drum increases the amount of startup waste may increase,particularly if a greater amount of vacuum is required for the largerdrum, leading to longer vacuum stabilization times. Larger drums thatrequire greater amounts of vacuum also may require more power to producethe necessary vacuum. It will be understood that these considerationsalso apply to embodiments of the invention in which the combining drum800 does not have target regions 1002, 1102, such as in the embodimentdepicted in FIG. 8.

It is preferred, therefore, that the drum diameter D₁ be selected sothat the drum's circumference is large enough that the parts of the corecomposite 348 are in contact with the vacuum long enough to properlydistribute the SAP without excessive vibrations, but small enough toprovide the required precision and a minimal amount of startup waste. Ithas been found that in a preferred embodiment, the diameter D₁ isselected so that the circumference is equal to between three and sevencore lengths X₁. In a preferred embodiment, the combining drum 800(whether it has target regions 1002, 1102 or not) has a diameter D₁ ofabout 6 inches to about 28 inches, and more preferably of about 9 inchesto about 20 inches, and most preferably of about 12 inches. In thisembodiment, the number of wasted cores caused by vacuum hysteresis orother startup-related issues has been found to be about 5 products perstartup, as compared to up to about 50 products per startup withconventional core forming processes. It has also been found thatproviding the necessary vacuum to such a combining drum 800 requiresabout 10 horsepower to 20 horsepower, whereas conventional core formingsystems require up to about 400 horsepower, and so a significant powersavings is provided.

Referring now to FIGS. 12 through 14, a preferred embodiment of thecombining drum is shown in which the combining drum 800 may beconfigured to apply a vacuum to the parts of the core composite 348 onlythrough a portion of the drum's rotation. The combining drum 800 of apreferred embodiment comprises an outer drum 1202 that is positioned torotate about a fixed inner drum 1204 by, for example, being affixed toan axle 1208 that passes through rotary bearings 1210 in the inner drum1204. Such bearings 1210 may be equipped to reduce or prevent theleakage of the vacuum through them. A vacuum is applied to the space1206 inside the inner drum by a vacuum port 810. The vacuum is conveyedto the outer drum's vacuum surface 804 by way of one or more passages1212 through the inner drum 1204 that are preferably located subadjacentthe path of the vacuum surface 804 of the outer drum 1202 to maximizethe strength of the vacuum applied through the vacuum surface 804. Itwill be understood by those skilled in the art that the inner drum 1204may be replaced by any vacuum chamber having one or more passages 1212that convey a vacuum to a location subadjacent all or part of the vacuumsurface 804.

Only those portions of the vacuum surface 804 that are immediatelyadjacent the passages 1212 receive a vacuum, so the duration andlocation of the vacuum's application may be modified by changing thesize, number, or location of the passages 1212. Referring specificallyto FIG. 13, the passages 1212 may be positioned through an arc of theinner drum 1204 that defines a vacuum zone Θ_(v). The leading edge ofthe vacuum zone 1302 is preferably located proximal to the point atwhich the first casing sheet supply 316 contacts the combining drum,which is designated as Location A in FIG. 3. The trailing edge of thevacuum zone 1304 is preferably located beyond (as the drum rotates) thepoint at which the second casing sheet supply 318 contacts the combiningdrum 800, which is designated as Location D in FIG. 3. Referring now toFIG. 14, it can be seen that those portions of the vacuum surface 804that are not adjacent the passages 1212 are effectively cut off from thepull of the vacuum. After the core composite 348 passes the trailingedge of the vacuum zone 1304 and reaches this blocked-off area it isreleased from the vacuum's hold and conveyed to other parts of theassembly line.

The size of the vacuum zone Θ_(v) may vary depending on where thevarious parts are desired to be assembled to form the core composite348. In a preferred embodiment, the vacuum zone Θ_(v) is about 45degrees to about 180 degrees, and more preferably is about 90 degrees toabout 160 degrees, and most preferably is about 140 degrees.

Various devices may be employed with the combining drum 800 to modulatethe location and amount of vacuum applied to the core composite 348. Inone embodiment, shown in FIG. 13, internal sleeves 1306 or other valvingmechanisms may be used to adjust the points at which the vacuum zoneΘ_(v) begins and ends. In another embodiment, shown in FIG. 12, otherinternal sleeves 1214 or other valving mechanisms may be used to narrowor widen the width of the vacuum zone Θ_(v), thereby effectivelynarrowing and widening the width W₁ of the vacuum surface 804. In stillanother embodiment, an internal sleeve or other valving mechanism may beused to reduce the vacuum level within all or part of the inner drum1204. Any of such sleeves and valving mechanisms may be actuated by acontrol system 320 under the guidance of an open- or closed-loopfeedback system. Greater or lesser amounts of vacuum may also be appliedin discrete portions of the vacuum zone Θ_(v). Other designs will beobvious to one skilled in the art based on the teachings providedherein.

A combining drum 800, as described herein, may be used with any SAPfeeding device that deposits SAP onto opened tow or other fibrousmaterials. The embodiments of the combining drum 800 described hereinhave been found to be particularly useful when used in conjunction withthe vibratory feeder 332 as described herein.

The present invention offers several advantages over previous SAPdepositing systems. In particular, the vibratory feeder 332 providesimproved control over the volume and placement of the SAP 326 in thefiber, preferably the opened tow 312, allowing greater control over theSAP distribution (and zoned absorbency) during transitional phases, suchas during machine startup, stopping and other speed changes, leading tofewer rejected products during such times. In addition, the vibratoryfeeder 332 and combining drum 800 provide improved SAP penetration intothe fiber, preferably the opened tow 312 or other core material, and animproved ability to selectively position the SAP to provide desirablezoned absorbency. The vibrator feeder 332 and combining drum 800 alsoprovide easier operation, as the various features of each device may beintegrated into a control system 320. Stull further, the vibratoryfeeder 332 and combining drum 800 are relatively simple and reliabledevices that require little maintenance or cleaning, thereby reducingthe operating cost of the machine. Another advantage of the vibratoryfeeder 332 and combining drum 800 is that they may be operated at highline speeds without detriment to the product quality. Other benefitswill be apparent to those skilled in the art based on the teachingsprovided herein.

In another embodiment, the present invention provides an apparatus andmethod for forming absorbent structures that have a single casing sheet.Single-sheet absorbent cores are manufactured with a single casing sheet(rather than multiple casing sheets, as described previously herein)that is wrapped around all or part of the absorbent core material. Theuse of a single casing sheet has been found to provide manufacturing andeconomic advantages over using multiple casing sheets because the singlesheet does not require slitting and rerouting, and can be bonded toitself at a single seam, rather than multiple seams as in the case ofmultiple casing sheets. As with multiple sheet cores, such single-sheetabsorbent structures may be used in any absorbent product, includinggarments, such as diapers and pull-on pants, catamenial devices,absorbent wipes or sheets, and so on. Although it is known tomanufacture conventional fluff pulp/SAP absorbent cores having a singlecasing sheet, it has been found that known methods and apparatuses forforming single-sheet core structures are not particularly useful forforming single-sheet core structures made using tow-based absorbentcores.

Referring now to FIGS. 16A and 16B, embodiments of single-sheetabsorbent structures that may be manufactured using the presentinvention are shown in cross-section. In FIG. 16A, the absorbentstructure is shown as it might appear when installed in an exemplaryabsorbent product, in FIG. 16B the structure is shown with the rest ofthe absorbent product omitted for clarity. The single-sheet absorbentstructure comprises a tow-based absorbent core 1606 wrapped in a singlecasing sheet 1618. As can be seen in FIGS. 16A and 16B, the casing sheet1618 initially may be wider than the absorbent core 1606, and thenfolded over the core 1606 to fully encase it. The embodiment of FIG. 16Ademonstrates a tri-fold design, in which the casing sheet 1618 is foldedat two locations to form three sheet portions. FIG. 16B demonstrates abi-fold design, in which the casing sheet 1618 is folded at one locationto form two sheet portions. The two ends 1618 a, 1618 b of the casingsheet 1618 may overlap one another so that the inside of one end 1618 babuts the outside of the other end 1618 a, as shown in FIG. 16A, or maybe pinch-seamed so that the two ends 1618 a, 1618 b abut one another ontheir interior sides, as shown in FIG. 16B. The ends 1618 a, 1618 b ofthe casing sheet 1618 also may abut one another without any substantialoverlap, or may be attached and some or all of the overlapping portionsremoved before final assembly into a product. Also, in any case, theseam may be located on the top, bottom or sides of the absorbent core1606, and may be unbonded or bonded (such as shown by bond 1622) usingany known or later-developed bonding technique. Various usefulcompositions of the tow-based absorbent core 1606 and casing sheet 1618have been described in more detail previously herein. In a preferredembodiment, the casing sheet 1618 comprises a sheet of tissue.

Other features of the exemplary garment 1600 of FIG. 16A include a fluidpervious topsheet 1602 and fluid impervious backsheet 1604. Garment 1600may also have fluid pervious or impervious waste containment flaps 1612,which may contain elastic members 1614, and leg elastics 1608 adjacentthe leg openings 1628 a, 1628 b to help control leakage. An additionallayer 1620, comprising a wicking layer or the like, may also be providedin the garment 1600, and may be located inside the casing sheet 1618,outside the casing sheet 1618, or between the overlapped ends 1618 a,1618 b of the casing sheet 1618. Useful materials and constructions forthese and other components of exemplary garment 1600 have been describedin more detail elsewhere herein.

It has been found that the present invention can be adapted to provide acontinuous supply of single-sheet, tow-based absorbent core structuresin an economical and effective manner. In the present invention, avacuum draw roll, such as those described elsewhere herein, is used inconjunction with angled surfaces and other folding devices to combinethe tow, SAP and casing sheet into a fully folded continuous supply ofabsorbent core composite material. From this continuous supply, a seriesof single-sheet absorbent structures may be cut to form individualabsorbent cores, which may be integrated into any type of absorbentarticle or device or used on their own. Various embodiments of thepresent invention are now described with reference to FIGS. 17-29.

In one embodiment of the present invention, shown in FIG. 17, a vacuumdraw roll 1708, is operated in conjunction with a tapered break drum1714 and folders 1716 to form and fold a single-sheet core compositesupply. In this embodiment, the materials required to form the absorbentstructure are provided to the apparatus by a tow supply mechanism 1702,a particulate matter supply mechanism 1704, and a casing sheet supplymechanism 1706. The tow supply mechanism 1702 may comprise any towconveying device that provides a supply of tow, such has rollers or thelike, and preferably comprises a tow forming jet, as describedpreviously herein. The tow 1703 may be any suitable tow, as describedabove, for forming an absorbent structure, and preferably is a celluloseacetate tow that is opened prior to or while being supplied to theapparatus of the present invention. The particulate matter supplymechanism 1704 provides SAP and/or other additives in particulate form(which may include powders, grains, flakes, microfibers and the like) tothe apparatus, and may comprise any conventional feed device, or morepreferably, a vibratory feeder, such as those described herein. Thecasing sheet supply mechanism 1706 is shown as a single roller, but maycomprise any sheet conveying device or devices, such as rollers, feedrolls, festoons, and the like, as are well known in the art, that arecapable of providing a casing sheet supply 1707 (preferably a sheet oftissue) in a controlled manner to the apparatus.

With respect to the vacuum draw roll 1708, the casing sheet supplymechanism 1706, the particulate matter supply mechanism 1704 and the towsupply mechanism 1702, the embodiment of FIG. 17 may operate in much thesame manner as the embodiments of these components described elsewhereherein, such as with reference to FIG. 3. More specifically, the vacuumdraw roll 1708 rotates about a first axis 1710 and pulls the opened tow1703 out of the tow supply mechanism 1702 and joins it with the casingsheet supply 1707. The particulate matter supply mechanism 1704 ispositioned to deposit SAP 1705 or other particulate additives to theopened tow before it is combined with the casing sheet supply 1707. Inaddition, a first adhesive applicator 1712 may be positioned to sprayadhesive on the portion of the casing sheet supply 1707 that contactsthe tow 1703 to provide adhesion between the tow 1703 and the casingsheet supply 1707, and to adhere the SAP 1705 in place. Of course, thesevarious components can be repositioned in various ways, and it isanticipated; for example, that the invention may be configured such thatthe particulate matter supply mechanism 1704 deposits the SAP 1705directly onto the casing sheet supply 1707 or such that the firstadhesive applicator 1712 sprays adhesive directly onto the tow 1703.

Like the other vacuum draw rolls and combining drums described elsewhereherein, the vacuum drum has a foraminous center surface (see FIGS. 8 and24) that applies a vacuum to the tow 1703 and casing sheet supply 1707.It has been found that relatively little vacuum is necessary, and avacuum of about 1 to 2 inches of water, and preferably 1.5 inches ofwater is adequate for high speed core forming operations. The foraminouscenter surface may be shaped to accommodate and convey the tow 1703, andmay be flat, rounded, angled, recessed and so on. In a preferredembodiment the foraminous center surface has a recessed portion, such asis shown in FIGS. 9 and 27. Other features and embodiments of the vacuumdraw roll 1708 are described in more detail elsewhere herein.

In the embodiment of FIG. 17, the casing sheet supply 1707, tow 1703 andSAP 1705 (or other particulate additives) are combined on the vacuumdraw roll 1708 into an unfolded open core composite supply 1718 that isopen on the side that faces the vacuum draw roll 1708. For the purposesof this disclosure, the term “open core composite supply” means anycomposite structure having a tow material on one side and a casing sheetmaterial on the other side, wherein the casing sheet material does notfully enclose the tow material (thus leaving the composite structure“open”). It should be noted that in this embodiment the tow 1703 is theonly material between the SAP 1705 and the foraminous surface and vacuumof the vacuum draw roll 1708. It has been found that the tow 1703 hasthe unexpected ability to act as a filter that provides sufficientresistance to impede the flow of the SAP 1705 and prevent the loss ofany substantial amount of SAP 1705 into the vacuum. After being formed,the open core composite supply 1718 preferably is transferred to avacuum conveyor 1726 for further processing.

It has been found that a significant amount of static electricity canaccumulate on the tow 1703 during the opening process when a tow formingjet is used. This static electricity can generate enough attractionbetween the vacuum draw roll 1714 and the open core composite supply1718 to cause undesirable clinging that can create irregularities in theoperating path of the open core composite supply 1718 and inhibit thespeed at which the apparatus can operate. In order to reduce oreliminate this static charge accumulation, water may be introduced inthe tow forming jet and/or on the vacuum draw roll 1714 to help reducestatic accumulation and facilitate the release of the open corecomposite supply from the vacuum draw roll 1714.

In other embodiments, an additional layer of material (not shown), suchas a wicking layer or acquisition layer may be placed on the vacuum drawroll 1708 either before or after the tow 1703 and/or casing sheet supply1717 is applied to the vacuum draw roll 1708. In these embodiments, theabsorbent core composite supply may be formed with an integral layer1620 being incorporated directly into the structure.

The casing sheet supply 1707, SAP 1705 and tow 1703 are formed into asubstantially flat and folded supply of core composite material in aprocess shown representatively by FIGS. 18A-18C. FIGS. 18A-18C arecross-sectional drawings of the core composite materials shown atreference lines 4—4, 5—5 and 6—6 in FIG. 17, respectively, with themachinery omitted for clarity. In the first step, the various materialsare combined together to form an open core composite supply 1718. In theembodiment of FIG. 17, the open core composite supply 1718 is providedin a substantially flat configuration, as shown in FIG. 18A. Next, asshown in FIG. 18B, the open core composite supply 1718 is folded so thatit has one or more obtuse angles Θ_(o) in it. Finally, thepartially-folded open core composite supply 1718 is fully folded so thatit is substantially flat, as shown in FIG. 18C. Although the embodimentshown in FIGS. 18A-18C depicts a tri-fold design, it will be appreciatedthat by using a single obtuse angle Θ_(o), a bi-fold design may be made.In other embodiments, such as those described subsequently herein withreference to FIGS. 21 to 27, the various steps described above,particularly the first and second steps, may be combined to improveefficiency, reduce apparatus size or obtain other benefits.

In the embodiment of FIGS. 18A-18C, The casing sheet supply 1707preferably is wider than the tow supply 1703 so that the ends of thecasing sheet supply can be folded over and joined to one another. Inthis embodiment, the casing sheet comprises three regions: a centerregion R₁ and first and second lateral regions R₂, R₃. The center regionR₁ is located approximately along the centerline of the casing sheetsupply 1707, while the first and second lateral regions R₂, R₃ arelocated on either side of the center region R₁. The edges of the centerregion R₁ are defined by the locations at which the obtuse angles Θ_(o)are made. It is also anticipated that the center region R₁ can be offsetto one side, and one or both of the lateral regions R₂, R₃ can be foldedto cover the tow to form the core composite as a bi-fold design (inwhich only one side region is folded) or a tri-fold design having anoffset seam.

The first adhesive applicator 1712, if used, applies adhesive 1802continuously or intermittently to the center region to adhere the tow tothe casing sheet supply 1707 and hold the SAP in place. The adhesive1802 may be applied in lines, swirls, bands or in any other usefulpattern. Adhesive preferably is not applied in the lateral regions R₂,R₃ during the initial assembly stages because such adhesive might adhereto the vacuum draw roll 1708 or other machinery and interfere withmanufacturing. As noted elsewhere herein, the type and amount ofadhesive should be selected to minimize any detriment to the absorbingcapability of the core composite, and standard construction adhesive mayapplied to the casing sheet supply 1707 by a standard melt blown sprayadhesive applicator. The selection of adhesives, whether hydrophobic orhydrophilic, and different types of applicators will be understood bythose of ordinary skill in the art. A suitable selection of adhesivesand applicators will be readily apparent without undue experimentation.

In a preferred embodiment, the obtuse angles Θ_(o) are formed in thecasing sheet supply 1707 outboard of the tow 1703, as shown in theFigures. It is also anticipated, however, that it may be useful to formthe obtuse angles Θ_(o) at locations slightly inboard of the edges ofthe tow 1703 so that the tow 1703 has thicker edges. In a bi-folddesign, the tow 1703 may also be folded along its centerline to form adouble-thickness structure.

The obtuse angles Θ_(o) may be formed in the open core composite supply1718 by breaking the open core composite supply 1718 using one or moreangled surfaces. In the embodiment of FIG. 17, the open core compositesupply 1718 is conveyed over a tapered break drum 1714 having anintegral pair of angled surfaces 1720. The tapered break drum is shownin more detail in FIG. 19. As shown in FIG. 19, the tapered break drum1714 comprises a center surface 1902 (which may be cylindrical, rounded,recessed or otherwise shaped or textured) and two angled surfaces 1720.The two angled surfaces 1720 extend from a respective edge 1904 of thecenter surface 1902 and taper (preferably in a conical fashion) to havea smaller diameter as they proceed away from the center surface 1902.The angle of the taper, is selected to impart the desired obtuse anglesΘ_(o) in the open core composite supply 1718. In order to minimizefriction on the open core composite supply 1718, the tapered break drum1714 preferably rotates about an axis 1906 so that the surface speed ofthe tapered break drum 1714 approximately matches that of the open corecomposite supply 1718, and is preferably designed to have a lowrotational inertia to allow the drum to quickly respond to changes inoperating speed. The tapered break drum 1714 is positioned in theassembly line such that it tends to create tension in the center regionR₁ of the open core composite supply 1718, as shown, for example, inFIG. 17. When the tapered break drum 1714 is thus positioned, the sideregions R₁, R₂, which are not under as much tension as the center regionR₁, tend to follow the path of least resistance by following thecontours of the angled surfaces 1720, thereby forming the obtuse anglesΘ_(o).

In another embodiment shown in FIG. 20, the angled surfaces may insteadcomprise rollers 2004 or fixed guides that are placed at angles adjacentto an untapered break drum 2002. In this embodiment, the break drum 2002applies tension to the center region R₁ of the open core compositesupply 1718, and the rollers 2004 impart the desired obtuse angles Θ₀ inthe side regions R₁, R₂ of the open core composite supply 1718.

The size of the obtuse angles Θ_(o) preferably are selected to increasethe speed at which the open core composite supply 1718 can be folded bythe folders 1716. This angle may depend on the type of folders 1716 thatare employed. It is also anticipated that in a tri-fold design theobtuse angles Θ_(o) may be different for each side of the open corecomposite supply. In a preferred embodiment, the obtuse angles Θ_(o) arebetween about 130 degrees and about 175 degrees. In a more preferredembodiment, the obtuse angles Θ_(o) are between about 140 degrees andabout 165 degrees. In an even more preferred embodiment, the obtuseangles Θ_(o) are about 154 degrees.

After the obtuse angle Θ_(o) or angles are made in the open corecomposite supply 1718, it is conveyed to one or more folders 1716 thatfold the composite into a substantially flat folded core compositesupply 1724. The folders 1716 may comprise any known folding equipment,but preferably comprise a set of folding boards that maintainsubstantially equal web tensions across the cross-direction of thetissue sheet (i.e., in the direction perpendicular to the machinedirection. Ideally, the folding boards prevent unwanted wrinkling orbuckling in the tissue sheet.

A second adhesive applicator 1722 may, in some embodiments, be providedto apply adhesive to the center or side regions R₁, R₂, R₃ during thefolding process to hold the casing sheet supply 1707 in place once thefolded core composite supply 1724 is formed. Such adhesive may beapplied on either side of the casing sheet supply 1707, and may also beapplied on the tow 1703. It will be appreciated that the design andlocation of the second adhesive applicator 1722 should be selected sothat it is operatively associated with the folder 1716 such that itapplies adhesive to the proper surfaces either before, during or afterthe folding operation performed by the folder 1716. The relativepositioning of these devices, and other manners in which the secondadhesive applicator 1722 may be operatively associated with the folder1716 will be readily understood by those of ordinary in the art. In apreferred embodiment, the second adhesive applicator 1722 comprises aslot-coater that applies construction adhesive to seal the casing sheetsupply 1707 after it is has been folded. The slot-coater preferablycomprises a blade-like device that slips between the overlappingportions of the casing sheet supply 1707 and applies adhesive to one orboth of the facing portions of the folded, but as yet unbonded, casingsheet supply 1707. Of course, the second adhesive applicator 1722 mayalso comprise any conventional adhesive applicator, such as a sprayadhesive applicator or conventional slot adhesive applicator positionedprior to or above the folder 1716 that applies adhesive before thecasing sheet supply 1707 is fully folded. After the adhesive is appliedby the second adhesive applicator 1722, the folded core composite supply1724 may be may be pressed in a pinch roller or in a debulker (notshown) to help seal the adhesive. Alternatively, or in addition to thesecond adhesive applicator 1722, other bonding devices or methods may beused. For example, in a bi-fold design, an edge sealer may be employedafter the second adhesive applicator to attach the edges of the casingsheet supply, as shown in FIG. 16B. In still other embodiments, thecasing sheet supply 1707 may not be sealed at this point, and mayinstead be held in its closed position by contact with other parts of agarment or other article into which the folded core composite supply1724 is integrated.

Referring now to FIG. 21, in another embodiment of the invention, theangled surfaces may be integrated into the vacuum draw roll, therebymaking the apparatus more compact and removing the necessity ofproviding a separate break roll or other devices between the vacuum drawroll and the folders 1716. In this embodiment the vacuum draw roll is atapered vacuum draw roll 2102 that comprises one or more angled surfaces2104. The tapered vacuum draw roll 2102 simultaneously forms the opencore composite supply 1718 and creates the obtuse angles Θ_(o) in theopen core composite supply 1718. A vacuum conveyor 2108 then transportsthe open core composite supply 1718 to the one or more folding devices1716 where it is folded into a folded core composite supply 1724. In avariation of the embodiment of FIG. 21, shown in FIG. 22, the vacuumconveyor 2108 may comprise an arcuate portion 2110 that wraps partiallyaround the tapered vacuum draw roll 2102. It is believed that in thisembodiment the presence of the arcuate portion of the conveyor may helpretain the SAP 1705 or other particulate matter or additives in positionduring the forming operation.

A tapered or stepped lay-on roll 2106 also may be used in conjunctionwith the embodiment of FIG. 21 to help conform the casing sheet supply1707 to the angled surfaces 2104 of the tapered vacuum draw roll 2102.An example of a tapered lay-on roll 2106 is shown in more detail in FIG.23. In the example of FIG. 23, the tapered lay-on roll has two taperedsurfaces 2302 that abut the angled surfaces 2104 of the vacuum draw rollduring use, and may optionally have a center surface 3204 having anappropriate shape (preferably cylindrical) to generally abut the centersurface of the tapered vacuum draw roll 2102. In other embodiments, thetapered surfaces may be replaced by one or more cylindrical or disc-likesurfaces.

An embodiment of a tapered vacuum draw roll of the present invention isnow described in detail with reference to FIGS. 24-27. FIG. 24 is anisometric view of a tapered vacuum draw roll 2402 showing the angledsurfaces 2404 (one of which is visible) and foraminous center surface2406. The angled surfaces 2404 and foraminous center surface 2406 aredisposed on a rotatable drum 2412 that is positioned outside an innerstructure 2408. The inner structure 2408 contains one or more vacuumpassages to convey a vacuum to the foraminous center surface 2406. Theangled surfaces 2404 preferably comprise tapered surfaces, preferablyshaped as conic sections, such as those described with reference to thetapered break drum 1714 of FIGS. 17 and 19. Also shown in FIG. 24 is avacuum port 2410 that may be connected to a vacuum source. Of course, itwill be appreciated that in embodiments of the invention in which abi-fold core design is produced, there may only be one angled surface2404, and the foraminous center surface 2406 may not be located in thecenter of the rotatable drum. Also in a bi-fold design, the centersurface may be peaked in the middle to break the open core compositesupply 1718 along or near its centerline.

Referring now to FIGS. 25 and 26, the internal structure of taperedvacuum draw roll 2402 is described. As noted before, the tapered vacuumdraw roll 2402 comprises a rotatable outer drum 2412 disposed around aninner structure 2408. For clarity, in FIG. 25 the outer drum 2412 isshown cut away at about the middle of the foraminous center surface 2406and the passages through the foraminous center surface 2406 are omittedin both FIGS. 25 and 26. In this embodiment, the inner structure 2408comprises a vacuum chamber 2414 to which a vacuum is provided. The innerstructure 2408 also has one or more vacuum passages 2418 that place thevacuum chamber 2414 in fluid communication with the underside of theforaminous center surface. As best seen in FIG. 26, there may be a space2420 between the foraminous center surface 2406 and the outer surface ofthe inner structure 2408. In order to prevent the vacuum from beingapplied the entire circumference of the foraminous center surface 2406,a pair of vacuum blocks 2422 are placed in the space 2420 to inhibit thefluid communication of the vacuum. As shown in FIG. 25, the placement ofthe vacuum blocks 2422 dictates the size of the vacuum zone Θ_(V) inwhich vacuum is applied to the foraminous center surface 2406.

In a preferred embodiment, the tapered vacuum draw roll 2402 (or anyother draw roll) may be further equipped with a pressurized air blow-offport to help remove the open core composite supply 1718 for furtherprocessing. In such an embodiment, the inner structure 2408 may furthercomprise a pressurized chamber 2416 to which pressurized air isprovided. The pressurized air in the pressurized chamber 2416 is placedin fluid communication with the foraminous center surface 2406 to expelthe open core composite supply 1718 after it reaches the trailing edgeof the vacuum zone Θ_(v). Preferably, this is accomplished by providingthe vacuum block located at the trailing edge of the vacuum zone Θ_(v)with an air blow-off passage 2424 that is in fluid communication withthe pressurized chamber 2416. As the outer drum 2412 rotates, theforaminous center surface 2406 passes over the blow-off passage 2424,and the pressurized air therein is forced out of the foraminous centersurface 2406, creating a force to release the open core composite supply1718.

The foraminous center surface 2406 may be any suitable surface havingholes or slots to pass a vacuum therethrough, and preferably is similarto the vacuum surface 804 described previously herein with reference toFIG. 8. Referring now to FIG. 27, in a preferred embodiment, theforaminous center surface comprises three vacuum regions: a centralvacuum region Z₁ and first and second lateral vacuum regions Z₂, Z₃. Thecentral vacuum region Z₁ preferably is approximately the same width asthe supply of tow material 1703, and is recessed to accommodate the tow1707 to some degree as it is being conveyed. The lateral vacuum regionsZ₂, Z₃, are disposed in either side of the central vacuum region Z₁, andcontact the casing sheet supply 1707 during operation. The purpose ofthe lateral vacuum regions Z₂, Z₃ is to firmly hold the casing sheetsupply 1707 to form a seal that inhibits the lateral escape of SAP 1705or other additives during operation, and to improve the grip on the tow1703 and casing sheet supply 1707 that is created in the central vacuumregion Z₁.

In many of the embodiments described previously herein (such as theembodiments described with reference to FIGS. 17, 21 and 22), the casingsheet supply 1707 is conveyed along a portion of its path by the vacuumdraw roll 1708, 2102 in such a manner that the casing sheet supply 1707wraps around a substantial portion of the vacuum draw roll 1708, 2102.However, in other embodiments, the various devices described herein canbe arranged in configurations in which a vacuum draw roll deposits towonto a casing sheet supply that is conveyed without being wrapped arounda portion of the vacuum draw roll 2808. Various embodiments having thisconfiguration are now described with reference to FIGS. 28 and 29.

Referring to FIG. 28, in one embodiment of the invention a casing sheetsupply may be provided by a substantially linear conveyor 2826(preferably a vacuum conveyor), while tow 2803 is provided by a towsupply mechanism 2802 and particulate matter such as SAP 2805 isprovided by a particulate matter supply mechanism 2804. As the casingsheet supply 2807 is conveyed along the conveyor 2826, a first adhesiveapplicator 2812 applies adhesive to all or part of one side of thecasing sheet supply 2807. Next, SAP 2805 is applied, and then the tow2803 is deposited onto the casing sheet supply 2807 by a vacuum drawroll 2808 to form an open core composite supply 2818. The open corecomposite supply 2818 is then conveyed to a folder 2816 that folds itinto a substantially flat, folded core composite supply 2824.

The first adhesive applicator 2812 applies adhesive to hold the SAP inplace and adhere the tow 2803 to the casing sheet supply 2807. A secondadhesive applicator 2822 may also be used with the embodiment of FIG. 28to apply adhesive to either the tow 2703 or casing sheet supply 2807 tohold the folded portions of the casing sheet supply 2807 in place afterit is formed into the folded core composite supply 2824. In anotherembodiment, the second adhesive applicator 2822 may be omitted if thefirst adhesive applicator 2812 is adapted to apply adhesive to theportions of the casing sheet supply 2807, such as the lateral regionsR₂, R₃, that will eventually be folded over to hold the folded corecomposite supply 2824 together. In an embodiment in which the firstadhesive applicator 2812 is used to apply adhesive to the lateralregions R₁, R₂ of the casing sheet supply, the vacuum draw roll 2808should be positioned so that it does not contact the portions of thecasing sheet supply 2807 that have adhesive applied to it in order toavoid accumulations of adhesive on the machinery. Of course othersealing devices, such as ultrasonic sealers, also may be used to form abond to hold the folded core composite supply 2824 together.

Embodiments in which the casing sheet supply 2807 is not conveyed aroundthe vacuum draw roll 2808 provide the advantage that the apparatus canbe reconfigured relatively easily to modify or supplement the assemblyprocess. For example, as shown in FIG. 29, a third adhesive applicator2813 may be included between the particulate matter supply mechanism2804 and the vacuum draw roll 2808 to provide another layer of adhesiveto hold the SAP 2805 in place and/or to adhere the tow 2803 to thecasing sheet supply 2807. In such an embodiment, the first adhesiveapplicator 2812 may optionally be omitted.

FIG. 29 also demonstrates other features that may be used with anyembodiment of the invention. For example, a second tow supply mechanism2802′ may be used in conjunction with the original tow supply mechanism2802 to provide a second supply of tow 2803′ and thereby create amulti-component or multi-layered tow. In such an embodiment the secondsupply of tow 2803′ may be placed under, above, or next to the originalsupply of tow 2803. Also shown in FIG. 29 are a second vacuum draw roll2828 and a fourth adhesive applicator 2834 that may be used to attach anadditional supply of tow 2832 to the folded core composite supply 2824.The additional supply of tow 2832 may be used, for example, as anacquisition layer or as a transfer layer, or may be infused with anadditional supply of SAP (not shown) to act as an additional absorbentlayer.

FIG. 29 also demonstrates an embossing roll 2836 that may be used inconjunction with the invention to emboss the casing sheet supply 2807.The pattern of the embossing roll 2836 may be selected to form wells,microwells or grooves in the surface of the casing sheet supply 2807.The SAP 2805 deposited on the casing sheet supply 2807 may concentratein these wells or grooves, thereby creating zones of greater or lesserabsorbency in the completed core composite supply 2824. These zones cansubsequently be positioned into absorbent garments to provide targetedregions of high absorbency. The embossing provided by the embossing roll2836 also may add loft or a more desirable texture to the structure ofthe finished absorbent garment or provide other benefits.

Although FIGS. 28 and 29 and the discussion thereof describe the casingsheet supply 2807 as being conveyed in a substantially linear fashion byconveyor 2826, it is also envisioned that conveyor 2826 may have anon-linear path, such as the conveyor 1726 in FIG. 17, with the vacuumdraw roll 2808 being located at the point at which conveyor 2826 isinverted or elsewhere. All such variations are within the scope of thepresent invention.

Although the tow supply mechanisms described thus far (i.e., items 1702,2802, 2802′ and 2830) have generally depicted tow forming jets, it willbe understood by those of ordinary skill in the art that the tow supplymechanisms may also comprise any other type of tow-forming ortow-supplying device. Indeed, there is no requirement that the tow beopened or otherwise conditioned “on the fly” during the manufacturingprocess. Instead, in other embodiments of the invention the tow may besubstantially fully prepared in a separate manufacturing operation, andsupplied to the present invention as a roll good. As used herein, “rollgood” refers to any pre-made supply of material that requires little orno further substantive processing as it is supplied to the presentinvention. A roll good preferably is provided in roll form, but also maybe provided as sheets, as a folded supply, as a continuous ordiscontinuous supply, or in any other suitable manner, as will beapparent to those of ordinary skill in the art.

FIG. 30 depicts an apparatus similar to that of FIG. 29, except that thetow supply mechanisms comprise various types of roll good tow supplymechanisms. As shown in FIG. 30, a first roll good tow supply 3003 thatforms the absorbent core 2824 may be provided as a continuous supplyfrom a wound reel 3002 of roll good tow material. A conventional tissueunwinding mechanism or other suitable device may be used to control thefeed rate of the first roll good tow supply 3003. Various rollers 3009may be used to convey the first roll good tow supply 3003 and press itto the casing sheet supply 2807. A second roll good tow supply 3032 alsomay be supplied to overlie the folded core composite supply 2824 to actas an acquisition layer, transfer layer or the like. In the embodimentof FIG. 30, the second roll good tow supply 3032 is severed intodiscrete pieces 3032′ that are spaced apart and placed onto the foldedcore composite supply 2824 using, for example, a conventional vacuumtransfer roll and cutting knife assembly 3028. Of course, the secondroll good tow supply 3032 may be provided by any other suitable device,and need not be provided as discontinuous pieces.

Other embodiments, uses, and advantages of the invention will beapparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein.Furthermore, the present invention may be used in combination with anysuitable prior art apparatus or methods, and any description herein ofdrawbacks or limitations of the prior art are not to be understood aslimiting the scope of the present invention to necessarily exclude theinclusion of such prior art apparatus or methods with the presentinvention. For example, it is envisioned that a second tissue layer orother casing layer may be used with the present invention to overlie theabsorbent core to provide additional tensile strength or fluid handlingcharacteristics. The specification should be considered exemplary only,and the scope of the invention is accordingly intended to be limitedonly by the following claims and equivalents thereof.

1. An apparatus for forming absorbent structures having a single casingsheet, the apparatus comprising: a tow supply mechanism for providingtow material; a particulate matter supply mechanism for providingparticulate matter; a casing sheet supply mechanism for providing casingsheet material; a vacuum draw roll comprising a foraminous centersurface, the foraminous center surface having a width defined by a firstedge and a second edge and being rotatable about a first axis, thevacuum draw roll being positioned to receive the tow material, theparticulate matter and the casing sheet material to form a open corecomposite supply; one or more angled surfaces positioned to create oneor more obtuse angles in the open core composite supply; and, one ormore folders to further fold the one or more obtuse angles in the opencore composite supply to form a folded core composite supply.
 2. Theapparatus of claim 1, wherein the tow material comprises celluloseacetate tow.
 3. The apparatus of claim 1, wherein the tow materialcomprises a roll good.
 4. The apparatus of claim 1, wherein theparticulate matter comprises superabsorbent particles.
 5. The apparatusof claim 1, wherein the casing sheet material comprises tissue.
 6. Theapparatus of claim 1, wherein the particulate matter supply mechanism isa vibratory feeder.
 7. The apparatus of claim 1, where in the tow supplymechanism is a tow forming jet.
 8. The apparatus of claim 1, wherein:the casing sheet material comprises a center region and first and secondside regions located on opposite sides of the center region, the firstside region extending from a first side of the center region to a firstedge of the casing sheet material, and the second side region extendingfrom a second side of the center region to a second edge of the casingsheet material; the casing sheet material is wider than the towmaterial; the tow material is positioned adjacent to the center regionof the casing sheet material in the open core composite supply; and, theone or more angled surfaces are positioned to create a first obtuseangle proximal to the first side of the center region, and a secondobtuse angle proximal to the second side of the center region.
 9. Theapparatus of claim 8, further comprising a first adhesive applicatorpositioned before the vacuum draw roll to apply adhesive to the centerregion of the casing sheet material.
 10. The apparatus of claim 8,further comprising a second adhesive applicator operatively associatedwith the one or more folders and positioned to apply adhesive to atleast one of the first and second side regions.
 11. The apparatus ofclaim 1, wherein the one or more angled surfaces are operativelyassociated with the vacuum draw roll.
 12. The apparatus of claim 11,wherein the one or more angled surfaces comprise first and secondtapering surfaces, each of the first and second tapering surfacesextending from a respective edge of the foraminous center surface andtapering inward from the center surface towards the first axis.
 13. Theapparatus of claim 1, further comprising a break drum positioned betweenthe vacuum draw roll and the one or more folders, the break drum beingrotatable about a second axis and comprising a center surface, thecenter surface having a width defined by a third edge and a fourth edge.14. The apparatus of claim 13, wherein the one or more angled surfacesare operatively associated with the break drum.
 15. The apparatus ofclaim 14, wherein the one or more angled surfaces comprise first andsecond tapering surfaces, each of the first and second tapering surfacesextending from a respective edge of the center surface and taperinginward from the center surface towards the second axis.
 16. Theapparatus of claim 1, further comprising an open core composite supplyconveyor, the open core composite supply conveyor being positioned toconvey the open core composite supply from the vacuum draw roll to theone or more folders.
 17. The apparatus of claim 16, wherein the opencore composite supply conveyor comprises an arcuate region substantiallyadjacent to a sector of the vacuum draw roll.
 18. The apparatus of claim1, wherein the vacuum draw roll further comprises: a rotatable outerdrum, wherein the foraminous center surface is disposed on the rotatableouter drum; and an inner structure disposed at least partially withinthe rotatable outer drum and comprising a vacuum chamber, the vacuumchamber having one or more vacuum passages forming a vacuum zonesubadjacent at least a portion of the foraminous center surface.
 19. Theapparatus of claim 18, wherein the one or more angled surfaces comprisefirst and second tapering surfaces, each of the first and secondtapering surfaces being disposed on the rotatable outer drum andextending from a respective edge of the foraminous center surface andtapering inward from the center surface towards the first axis.
 20. Theapparatus of claim 18, wherein the vacuum zone comprises a leading edgerelative to a direction of rotation of the rotatable outer drum and atrailing edge relative to a direction of rotation of the rotatable outerdrum, and the inner structure further comprises a positive air blow-offport located proximal to the trailing edge.
 21. The apparatus of claim18, wherein the foraminous center surface comprises a central vacuumregion and first and second lateral vacuum regions, the first lateralvacuum region being located between the central vacuum region and thefirst edge of the foraminous center surface, and the second lateralvacuum region being located between the central vacuum region and thesecond edge of the foraminous center surface.
 22. The apparatus of claim21, wherein the central vacuum region is recessed.
 23. The apparatus ofclaim 21, wherein the tow material has an average width approximatelyequal to or less than a width of the central vacuum region, and thecentral vacuum region is positioned to receive substantially the entirewidth of the tow material.
 24. The apparatus of claim 23, wherein thefirst and second lateral vacuum regions are positioned to apply a vacuumto the casing sheet material.
 25. A method for preparing absorbentstructures having a single casing sheet, the method comprising:providing tow material; providing particulate matter; providing casingsheet material; forming an open core composite supply by combining thetow material, the particulate matter and the casing sheet material on avacuum draw roll comprising a foraminous center surface, the foraminouscenter surface having a width defined by a first edge and a second edgeand being rotatable about a first axis; creating one or more obtuseangles in the open core composite supply using one or more angledsurfaces; and, forming a folded core composite supply by folding flatthe one or more obtuse angles in the open core composite supply.
 26. Themethod of claim 25, wherein providing tow material comprises providingcellulose acetate tow.
 27. The method of claim 25, wherein providing towmaterial comprises providing roll good tow material.
 28. The apparatusof claim 25, wherein providing particulate matter comprises providingsuperabsorbent particles.
 29. The method of claim 25, wherein providingcasing sheet material comprises providing tissue.
 30. The method ofclaim 25, wherein: providing casing sheet material comprises providingcasing sheet material comprising a center region and first and secondside regions located on opposite sides of the center region, the firstside region extending from a first side of the center region to a firstedge of the casing sheet material, and the second side region extendingfrom a second side of the center region to a second edge of the casingsheet material; providing tow material comprises providing tow materialhaving a width narrower than a width of the casing sheet material;forming the open core composite supply further comprises positioning thetow material adjacent to the center region of the casing sheet material;and, creating one or more obtuse angles in the open core compositesupply further comprises creating a first obtuse angles proximal to thefirst side of the center region, and a second obtuse angle proximal tothe second side of the center region.
 31. The method of claim 30,further comprising applying adhesive to the center region before formingthe open core composite supply.
 32. The method of claim 30, furthercomprising applying adhesive to at least one of the first and secondside regions before forming the folded core composite supply.
 33. Themethod of claim 25, wherein forming an open core composite supply andcreating one or more obtuse angles are performed simultaneously.